Chapter+2

toc

Section 1
**Sports article HW:** 11/3/10 The article that I read was titled "Study Explains Science of Soccer." In the article, Goff, a scientist explains how soccer isn't just a sport to him it is an art of physics where equations appear non-stop. He says that there is a physics to make the ball do things that seem to go against the laws of nature. He says it has to do with the air dynamic and the surface of the ball. He says that the less dense the air is, the more interesting the moves can become. It adds more trajectory. The speed of the ball also affects what you can do with it. He explains that there is a lot of physics that is put into soccer.

"Study Explains Science of Soccer." E! Science News Thursday July 2010. Print. http://esciencenews.com/articles/2010/07/01/study.explains.science.soccer

**What do you see?** **11/8/10** I see that the people who are running before kicking the ball will kick it farther. The more momentum, the farther it goes. The smaller people and animals like ladybugs for example can't kick it as far as the running bigger person.

**What do you think?** **11/8/10** I think that figure skaters keep moving across the ice at high speeds while not showing much effort because there is little friction when they are on the ice. It might also be dependent on the mass of the skater and the velocity. A soccer ball can keep rolling because of the force that is added on it and also because of the shape of the ball. It is also off the ground for a certain amount of time so there isn't friction added to stop the ball.

**Investigate: Newton's First Law** **11/8/10** 1c.) 5.49 meters  1e.) 5.49 meters 2a.) I think his highest point will be 5.49 meters. 2b.) I think this because he is starting at the same slope as before. The slope from his original starting point hasn't changed therefore his hight won't. 3a.) My answer of 5.49 meters was correct. I think my prediction was close and accurate because his slope didn't change yet so there was the same amount of gravity and force pushing him to go that far up on the other side of the slope. Once the slope is steeper, the skateboarder will go up farther. He has more momentum.  3b.) The ball stopped at exactly 5.49 meters. It was at the same height as the skateboarder was. 4a.) If there is a less steep slope, the height will decrease. There won't be as much force pushing the person to go farther. At the same time, there will be more gravity on the person and they wont go as far up. 4b.) My prediction was correct. As the slope decreased, the maximum height of the skateboarder decreased. He didn't go as high up and I also noticed that he went slower. 5a.) No matter how high up the person rolls he will never recover his starting height. This is because he will lose all his momentum after skating on flat ground. 5b.) The skater would roll as far as he can go after going off the track. He has nothing stopping him except gravity so he will go pretty far. He landed off the course. 5c.) Gravity and inertia would keep him on the track. 5d.) In the stimulation the skater rolls off the screen. He keeps going straight and will eventually stop because of gravity. 6a.) As the slope decreases the length decreases because the rider cant go up as far. He will also go slower and stop easier. 6b.) The final vertical position decreases. It will get lower as the slope decreases because there isn't as much momentum keeping the skateboard going. 6c.) The vertical position of the ball will be the same if the two sides have the same slope, however as the slope decreases the vertical position will as well. They are all dependent on each other. 6d.) The skater wouldn't stop because the track would keep going and there is nothing there to stop it. WIthout friction the skater will keep going forever.

**Physics Talk Summary** The Physics Talk is about Galileo a famous scientist who realized that a ball in motion on a ramp will obtain the same height when it is going up a new ramp with the same slope at the same speed. A ball moving on flat smooth land with no friction will travel forever. He developed the law of inertia, which stated that at object at rest will stay at rest, or an object in motion will stay in motion until a force,which is a push or pull, acts upon it. Newton used this to create his first law of motion which stated the same thing, without a force acting upon it an object will stay in motion or stay at rest on a **straight path**. He decided that an objects mass was dependent on its inertia, therefore, the greater the mass, the greater the inertia. This applies to sports because it gives a reasonable explanation for running starts. With one, the distance of an object will go farther and it will go faster. The speed of something is the distance over the unit of time. The velocity is the speed in a given direction, and the acceleration is the change in speed over a unit of time. The frame of reference is a vantage point with respect to which position and motion may be described. Its the perspective. If you throw a ball after running for example, the ball will be going at the speed that you throw it plus the additional speed it gets from you running.

**Checking Up Questions** 1.) Inertia is defined as the natural tendency of an object in motion to stay in motion or an object at rest to stay at rest until a force acts upon it. 2.) Newtons first law of motion is the same thing as inertia. It says that an object in motion will stay in motion and an object in rest will stay at rest until a force acts upon it with a constant speed in a straight line path. 3.) A force like friction needs to act upon it. A force is a push or a pull. 4.) A ball will not roll forever in the real world because of friction which is a force that stops it from, rolling. There is friction on the ground. 5.) The object with the larger mass will have a bigger inertia. They are directly dependent. 6.) It is important to establish the frame of reference because your ball will be going at the speed that you throw it at plus an additional speed which is added on which is dependent on the speed of the train.

11/9/10
 * Notes**
 * Inertia is a property of matter that measueres the resistance to changes in an object's motion.
 * __Mass__ is how you measure inertia. Weight has to do with gravity mass doesn't. Mass is how much stuff something is made of. Mass's base unit is kilograms

1a.) The ball will roll forever. 1b.) It will continue rolling forever because there is no force or friction to stop it, therefore, it will continue rolling in a straight path at a constant sped. 2.) It will reach 20 cm as well. Because the two slopes are the same and there is no friction the ball will go up the same height. 3.) I do not think its possible in the real world to do this. In the real world there is friction everywhere and this friction no matter how little will eventually stop something from rolling. 4.) The hockey puck is moved by the force exerted from the stick of the player. It will go however fast the player was moving before to how fast it was hit. Because there is barely any friction on the ice the puck will probably keep going until it hits a wall. 5.) 2.5 +4.5 = 7 m/s 7 m/s because they are standing still while the wagon as well as the ball are being pushed forward 6.) 4.2 m/s +10.3 m/s = 14.5 14.5 m/s because the the runner is going at a speed of 4.2 and then you need to account for the 10.3 m/s that he throws it at.  7a.) 5.6+ 2.4= 8 m/s *work at bottom 8 m/s because the cart is going as fast as the train is and at the same time it is moving an additional speed. 7b.)5.6 - 2.4 = 3.2 m/s 3.2 m/s because you are already moving at the speed of 5.6 so you don't need to account for the speed of the train.  7c.) 6.1 m/s at 67 degrees 8.) 85- 18= 67 m/s 67 m/s because the arrow started already at 18 m/s so you need to take it out of the speed.  9a.) 21.2 m/s *work at bottom 9b.) 43.9 cm *work at bottom 9c.) 58 cm *work at bottom 9d.) 172 cm *work at bottom 10 a and b.) In hockey, the puck will continue to glide across the ice until it hits a wall. There is barely any friction to stop it. WHen you skateboard on a ramp, unless there is friction, the skateboard will keep going at the same height. When you are playing soccer and taking a goal kick, the ball will remain unmoved until you kick it. The kick is a force.
 * Physics To Go**

**What do You Think Now?** **11/9/10**

Figure skaters are able to skate across the ice with little effort because of inertia. If there isn't a lot of friction, an object in motion is able to stay in a straight path in motion. Because there is a little friction though, they eventually will need to exert some effort. A soccer ball is able to roll across the field after being kicked because of the force exerted on the ball from the kick. THe ball is going at a high speed because of the person running with it as well as its individual speed. It will take a while to slow down.


 * Inquiring Further**
 * 11/10/10**

The object of curling is the move your stones down a sheet of ice and push it into your target of concentric circles. You and a partner pushes it down the ice. This relates to Newtons first law of motion because the stones glide down the ice and keep going in the a straight path. Unfortunately there is an unbalanced force which is friction which will eventually stop the stone. Like Newton said though, the stone will continue to glide until friction stops it. I got the information from http://scienceblogs.com/builtonfacts/2010/02/the_physics_of_curling.php

**Section 2**
**What do You See?** **11/9/10**

In this picture i see a boy who is walking slow. His footprints are spread out at a constant normal pace and there is little distance in between the steps. In the next picture there is a boy who is running really fast. You can tell because of the wind and also because of the footprints in back of him. They are all spread out pretty far apart.

**What do you Think?**

100 miles an hour to me shows that something is averaging a specific speed. In 1 hour, that object or person can travel 100 miles. It is about the equivalent of 44.7 m/s. 45 meters per second means that you can go 45 meters in a second. As you can see they are both the same speed just in different units.

**Constant Speeds Sports HW** 1. In skating you keep a constant speed because you are gliding along this ice. Without a constant speed and straight path, the skater would probably not look as graceful. 2. In soccer you need to keep a constant motion when going up and down the field. It is also easier to control the ball if you go at a constant speed because you won't get ahead or in back of the ball. 3. When you are running a track it is better to keep a constant speed and motion so you don't get ahead of yourself.


 * Physics Talk Summary**
 * 11/10/10**

As we learned before, acceleration is the change in speed over a unit of time. At a constant speed, footprints would be spread apart at the same lengths between each one. The faster you walk at a constant speed, the farther away the footprints will be. When you're accelerating, the spaces in between them will either increase which is positive acceleration or decrease which is negative. Average speed is the distance traveled divided by the time taken to travel that distance. It can be written as Vav= delta D over delta t. Instantaneous speed is different, it is the speed that you are traveling at a specific moment. To calculate the acceleration, you can write it as Acceleration equals the change in velocity over the change in time. The units are m/s squared.

**Checking Up Questions**

1a.) The dots would be equally spread apart 1b.) The space in between the dots would gradually increase 1c.) The space in between the dots would gradually decrease. 2.) Vav= delta D/ delta t  Vav= 400/50 Vav= 8 m/s 3.) Average speed is the speed that is taken from the total distance and the total time. It is a constant speed for the entire trip. Instantaneous speed is the speed you are driving at a certain time. 4.) Acceleration= Change in speed/ Change in time Acceleration = 100/10 Acceleration = 10 m/s squared

**Physics to Go** **11/12/10** 1.) Average speed is the average speed that a person is traveling over a whole distance over a unit of time. It is not a completely accurate speed. Instantaneous speed is the speed that you are traveling at on specific time.  2a.)Vav= 1 km/ 15 s  Average speed = .06 km/s --> 60 m/s 2b.) Vav= 84 m/ 6s Average speed= 14 m/s  2c.) Vav= 9.6 km/ 7200 s  Vav= 960 meters/ 7200 s  Average speed = 4.8 m/s 2d.) Vav= 400 km/ 4.5 h Average speed= 88.89 km/h  3a.) Negative acceleration- he is slowing down once he falls. 3b.) Positive acceleration- he is starting from at rest and his speed is gradually increasing. 3c.) No acceleration there is a constant speed. 3d.) Negative acceleration- the ball is going fast and once it is caught it is stopped. 3e.) No acceleration- it is constant. 3f.) No acceleration 4a.) Picture d and a  4b.) Picture b  4c.) Picture a  4d.) Picture c  4e.) A- positive b- no acceleration c- increasing then decreasing d- positive 6a.) A= (Vf- Vi)/t A= 0-45 km/h / 9s  45 km/ h x 1000m/ 1km x 1 h/ 3600 s  0-12.5 m/s / 9  a= -1.4 m/s ^2  6b.) Negative value. 7a.) Constant 7b.) Increasing speed 7c.) slow constant Increasing then constant then decreasing 7d.) decreasing then constant then increasing 8.) Vav= 100mi /2 h Average speed= 50 mph  9.) No, if his average speed is 15 m/s going to work, it is not his instantaneous speed. For example, he could have been traveling at 14 m/s for part of the trip and then 16 mph the other part of it. 10.) .x..x...x....x........x..............x...............x.......................x.......................x 11.) acceleration= change in velcity/ change in time Acceleration= 4 m/s / 5s Acceleration= .8 m/s squared 14a.) A soccer player dribbling the ball down the field is going at an average pace. He can't go to fast or too slow or he will lose control of the ball. 14b.) A runner in the middle of a race. He is going at a constant speed but as fast as he can go. 14c.) A point guard bring up a ball in a basketball game. They are moving at a slow constant pace while dribbling the ball up until they pass it. 14d.) A runner starting off a race is no moving but keeps going faster as time goes on until he reaches his fastest 14e.) After a runner crosses the finish line he slows down all the way to a stop.

11/16/10 1 and 2) 3a.) -5 m/s^2 3b.) -5 m/s ^2 3c.) -5 m/s ^2 *It is a constant speed for the whole trip from when the ball is dropped to when it bounces back up.
 * Physics Plus**
 * **Velocity** || **Acceleration** || **Example** ||
 * small || small || turtle, throwing a ball ||
 * big || big || race car, airplane, rocket ||
 * small || big || deer, dog, rabbit, rebounding(ex:ball against wall) ||
 * big || small || truck ||

**What do you Think Now?** 11/15/10

45 meters per second is equivalent to 100 miles per hour. The difference in the two though is the unit of measurement for distance and time. In one, you are going 45 meters in 1 second. In the other you are traveling 100 miles in an hour. Meters are a short unit of measurement than miles which is why you are able to go farther in a shorter amount of time.

Section 3
11/16/10

The person is pushing the ball and as time goes on it is going faster and faster as she's pulling it. You can see this because it is getting harder for her and the dog to keep up with the ball as it rolls.
 * What do you see?**

A force is a push or a pull. It is something that affects an object. The same amount of force will affect a tennis ball and a bowling ball differently because it will not push the bowling ball at the same speed as the tennis ball. The bowling ball will need more force to go as fast as the tennis ball because of its weight. It has more weight so a force won't push it as far or fast.
 * What do you Think?**

11/16/10
 * Physics Talk**

Newtons Second law is acceleration= force/ mass. Force is in Newtons, and mass is in kilograms. acceleration is m/s squared like usual. His law shows that acceleration is caused from unbalanced forces. The smaller the object is in mass, the acceleration will be higher, and as the forces become stronger, the acceleration is higher. Newton's law might not exist if the mass is to big and there isn't a lot of force. The acceleration is to small to measure. It always exists though its just hard to measure. Gravity can be a force and if there is acceleration there has to be an unbalanced force according to Newton. Weight is an unbalanced downward force exerted on a mass as a result of gravity. W=mg will help you find weight. W= weight, M= Mass, and G= gravity. A free body diagram helps determine net force. It shows the size and direction of the force acting on an object. If they are in the same direction the sum will be a bigger acceleration than each one. If they are in opposite directions there might be zero acceleration. For example if you are holding something, the arrows would be in different directions causing zero acceleration. If something is at a constant speed the arrows are in different directions. Free body diagram:

1.) Newton's second law states that there can't be acceleration without an unbalanced force. It is dependent on the force and the mass of the object that might make the acceleration bigger or smaller. 2.) Increasing the mass with a constant force will make the acceleration smaller because you will need more force to make it go faster. 3.) If an object weights 30 newtons, it means that its mass multiplied by the force of gravity exerted on the object is 30. 4.) If you went to a planet with higher acceleration, you would weigh less. This is because the higher the acceleration, the lighter the mass is. You would need less force to accelerate.
 * Checking up Questions**

11/18/10
 * Physics To Go**

1.) F= 350 N  m= 80 kg  A= 10 m/s squared  m=80 kg  a= -15 m/s squared  F= -3000 N  3.) A= F/ M  A=42 n/ .30 kg  A= 140 m/s squared 4.) A= F/M 20= F/ 0.040  F= .8 N  5a.) People would rather catch a baseball than a bowling ball because the bowling ball is going to stay in motion until you stop it and because of its mass if is harder to catch and stop. 5b.) Most people would rather catch a baseball at the same speed as a bowling ball flying because of its mass. There is a lot more mass and a lot more force on the bowling ball than the baseball making it harder to catch. 9.) The force is still on the ball from your hand until it is caught or stopped by someone or something else. 10.) The unbalanced force is the push that sarah and are putting on the desk. The net force is 90 Newtons. 11.) 200 n x 4 people= 800 N. The total net force is 200 newtons per person. If there are 4 people with the same force they are multiplied together to get 800 newtons. 12.) A= F/ M 125/.7  A= 179 m/s squared  13.) 120 N north -- 50 Newtons East 120^2 +50^2 = C^2 130 Newtons north at 67 degrees 14.) Hit with 4000 Newtons from north and 5000 newtons from the east 4000+5000= 9000  6403 N at 51 degrees North East  15.) A= F/M 9.8= F/ 12.8 A= 125 Newtons 16a.) 70 newtons northeast 16b.) A= F/ M  A= 10/5.6 A= 1.8 m/s squared 17a.) R= the square root of 30 ^2 + 20 ^2 The net force is 36 newtons  17b.) F= MA  3g= 100a A= .36 m/s squared 17c.) If they were both to the left the force would be 50 newtons. The new acceleration would be: A= F/M  A= 50/100  A= .5 m/s squared  18.) The player out on the soccer field is given a penalty kick. The ball, weighing around .43 kg and starting at rest is kicked by the player at a speed of 33 m/s squared and flies straight into the net. The force added on this ball from the player is around 14.19 newtons.

11/22/10
 * Active Physics Plus**

1.) 125 N- given traveling northwest- given tan^-1 = 125/125  tan^-1= 45 degrees  125 m/s Northwest at 45 degrees.  2a.) The net force is 30 N south 2b.) 81 N 2c.) The direction is Northwest

A force is a push or a pull. Without forces, objects wouldn't be able to move. It is defined as the mass times the acceleration of a specific object. The same amount of force will not do the same thing to a bowling ball as it does to the tennis ball because the tennis ball has less mass than a bowling ball. WIth the same amount of force, the acceleration of the tennis ball will be bigger than the acceleration of the bowling ball. A tennis ball needs less force to accelerate.
 * What do you Think Now?**

Section 4
11/23/10

The boy is timing the fall of the apples. The red and green apples are at the same level across. The green apple is projectile and curving the red apples are just dropping.
 * What do you see?**

**What do you think?** I think that the force at which you throw the object will determine how far the ball is going to go. The angle of the throw might also determine how far its going as well as the velocity and the speed of the object.

**Physics Talk Notes** The trajectory is the path that something is falling or being thrown at. A projectile is an object acted on ONLY by gravity. The X component and Y component of all vectors are independent. X components aren't affected by y components for example. Y-vertical velocities affect vertical distances. X- horizontal velocities affect horizontal distance. The time it takes for a horizontally launched projectile to hit the ground (hang time) is the same as the time it takes to drop. Acceleration due to gravity is -9.8 m/s squared. Horizontal velocity does not ever change, vertical velocity does. Vy- velocity at its maximum is always. Throwing horizontally results in the same trajectory as the second half of the path of ball thrown at an angle.

**Checking up Questions** 1.) They will reach the ground at the same time because with the exception of air resistance all objects fall at the same speed. They are at the same height and dropped at the same accelertaiton 2.) It increases by about 10 m/s every second 3.) THe velocity is 0 and the acceleration is 9.8 m/s squared.

**Physics to Go** 1.)

2.) 4.) Most people that I asked thought that the bullet being dropped would hit the ground before the horizontally shot bullet because of the speed it is being shot at. They didn't account for the fact that all objects fall at the same speed and that they are starting at the same height. 6.) Horizontal motion has no affect on vertical motion because it takes time for a horizontally launched projectile to hit the ground while in the air. Things like gravity only affect the vertical motion. 7.) A and B will hit the ground at the same time. They are both dropped or shot from the same height and the bow is being shot horizontally. 8.) 114.01 m/s *work after 9  9a.)11.3 m/s 9b.)v=d/t 11.3=d/2  d= 22.6 meters  10a.) 12 m/s 10b.) 4.25 meters 11.) The first pitch was just released from the pitchers hand. It was pitched horizontally at a speed of 40 m/s. THe batter hits the ball into the outfield at an angle of 37 degrees. The ball then drops and the velocity gets higher as it falls.

11/30/10
 * Active Physics Plus**

Sports Video Clip 11/28/10

This video clip shows the trajectory of a baseball being hit with a certain velocity and angle without air resistance: [] 1.) The ball in this situation is not hit in a horizontal motion. It is his at an angle. This affects the trajectory because it affects the speeds that the ball is traveling at. The ball is now losing speed and then gaining speed as it falls back down to the ground. The ball is being hit vertically because it goes up and then comes back down. 2.) The shape of the trajectory plays a part in the game because the shape of it shows how far the ball will travel. It shows how fast the ball will go and how high it will go. In this video clip, the ball is traveling in a curve. It is accelerating, which shows you the path of the ball.

**What do you think Now?** The distance that a ball travels after it is thrown is depended on the speed that it is thrown at as well as the angle that it is thrown at. As the angle gets bigger before 45 degrees, it will go pretty far. After 45 degrees, as the angle gets bigger, the ball wont travel as far. Also as the speed gets higher, it will travel farther.

Section 5
12/1/10

**What do you See?** A soccer ball is being kicked up in the air at a very big angle, Because this angle is so big, the ball isn't traveling very far but it is going very high. A little boy then heads the ball at a smaller angle less then 45 degrees. The ball is traveling a lot farther but not going as high up. the picture shows the trajectory of the ball.

**What do you Think?** As the angle gets bigger, the ball with go farther, up to 45 degrees. At 45 degrees an object will go the farthest it can at the same speed. After 45 degrees, the ball with started to go less of a distance each time. Complementary angles have the same range for a ground to ground launch. If an object is launched at the same angle, the higher the launch speed is, the farther it will go.

Projectiles have two motions, but each don't affect each other. They can accelerate at 9.8 m/s squared because of gravity or they can move at a constant speed. This helps understand trajectory. Physical models (picture of a ball rising and falling) and mathematical models(charts) show how a ball moves. When you forget about air resistance, a ball show be thrown in the form of a parabola, rising and falling. The ball will go a certain distance depending on the angle it is thrown at. If the angle is to small or to big, the ball wont go very far. A 45 degree throw will go the farthest. Small angles have the biggest horizontal velocities but have shorter time in the air. In the real world balls aren't thrown in a parabola because of air resistance.
 * Physics Talk Summary**

1.) Constant motion and acceleration help you understand the trajectory of a projectile. 2.) The fundamental requirement a scientist must meet is launch angle, launch speed, launch height, and the range. 3.) From 10 to 44 degrees the ball goes a farther distance each time. At 45 degrees the ball is the farthest it will go, and then the angles get smaller each time from 46 degrees to 80. All of them are in parabola forms because air resistance isn't included.
 * Checking Up Questions**


 * Physics Plus**

12/2/10 1.) 45 degrees because the object will go the farthest it can. 2a.) The bigger the angle is that is greater than 45 degrees, the less far the object will go  2b.) As the angle gets bigger before it hits 45 degrees, the object will go farther.  3a.) 90- 30 = 60 degrees 3b.) 90- 15= 75 degrees 4.) I think this occurs because most people can run faster than they can jump high. If she runs really fast before hand, she will have a bigger range without jumping at a 45 degree angle. 5.) I think that he was successful in his events because if he goes his highest velocity. He has a great horizontal velocity when he is running before hand and he is also good at launching himself upward at a fast speed. 6a.) The balls acceleration is -9.8 m/s squared. 6b.) The direction of the balls velocity at point x is downward. 7a.) V= Vi +at (-9.8) (3) = 29.4 m/s Speed: 29.4 m/s 7b.) 5 m/s 7c.) 15 meters 8.) The angle would have to be 45 degrees to travel the farthest distance. 9.) The biggest angle would be close to 90. 10a.) The acceleration is downward. (-9.8 m/s squared) 10b.) 4.5 seconds 10c.) 90 meters
 * Physics To Go**

**﻿What do You Think Now?** DIfferent angle measures change the range of how far something will go. If an angle is less than 45 degrees, then as the angle measure gets bigger, it will go father. Anything higher than 45 degrees goes less far each time. As the angle measures increase up to 90 degrees though, the projectile will get farther. As the speed of something increases though, the projectile will go farther. As the launch speed increases, the final velocity increases. The object travels in a parabola like form, so the faster it is going originally, the faster it will land because it has the same acceleration going up as it has going down.

Section 6
12/9/10

There is a boy pushing off a wall and going backwards. He is bending his legs so he is able to kick off better and go faster and farther. He starts off not moving and then after pushing off he is probably accelerating.
 * What do You See?**

To jump the highest you can, I would suggest bending your knees as much as possible and pushing off the ground the hardest you can. Apply force to the ground.
 * What Do You Think?**

12/13/10 When someone is pushing against the wall, they go backwards due to their leg movement. It is like the wall is pushing and forcing them to move back. The wall is pushing the person in the sense that their legs give a horizontal push which is forcing them to move away. There wouldn't be movement without the wall. When to people push on each other they both accelerate backwards because of the force of the other person. When you are walking, the force you add to the ground is the same that the ground adds to you. The forces are opposite in direction, making you accelerate forward. Newtons 3rd law says: for every force, there is an opposite and equal force acting back. They always act on different objects. The examples before show this like a person walking applies force to the floor and the floor applies force back. A free body diagram lets you see what forces are acting on an object. Forces are represented by arrows, and the size represents how much force. You are held down by your mass. If you are standing on the floor, it bends a little which is where it pushes you back up. The bend isn't noticeable. Newton first wrote his law in the book //Principa. Because of things like traction and friction, this law doesn't always apply. Situations like person pulling a chair on wheels doesn't apply because the forces aren't equal. There are two forces acting on the person and one on the chair which is why it doesn't fit Newton's law. //
 * Physics Talk**

1.) Newtons third law says that for every force applied, there is an equal and opposite force being applied back. 2.) A normal force is the opposite force. 3.) A free body diagram shows all the forces and how they are acting on an object. The forces are represented by arrows, and the longer they are, the more force is being added.
 * Checking up Questions**

**Physics To Go** 11/14/10

1.) The force from the shot put is equal to the force of the person's hand, but the force is in the opposite direction. 2.) The chair "knows" how hard to push on the person because of the normal force exerted on the chair from the ground. Because the objects aren't moving, there is no acceleration which means that the force applied for all of them will be equal. There is deflection on the floor because of the chair, and there is deflection on the chair because of the mass of the person. They balance out the force. 3.) A bathroom scale works because there is a spring inside which compresses when a person steps on the scale. 4.) The force of the ball on the bat, and the bat on the ball is equal, but in opposite directions. The bat's force is towards the ball and the ball is towards the bat. The bat probably sometimes breaks because of too much force from the ball. 5.) If a big linebacker tackles a small running back, they both experience the same force, but because the smaller player has a bigger mass, he has a bigger acceleration. 6.) When a hockey player hits the wall, he has normal force and weight from gravity. The normal force is both from the ground and towards the wall. The weight from gravity's arrow is pointing downward. The forces are equal but opposite. 7.) They like wearing gloves because the higher the acceleration of the ball, the bigger force it has. The bigger the force, and the faster that the ball is landing, makes it harder to catch. The ball will hit the person's hand a lot harder, and the glove protects that. 8a.) The quarterback throws the ball. The player catches it and runs down the field with the ball. An larger sized and bigger massed person tackles the player. The two players exert equal force on the other and they both go backwards. There forces were opposite but equal. 8b.) Deflection on the ground can produce a normal force. When a person is running, each step they take, they are deflecting the ground. The ground is being pushed back, and therefore, pushing them forward.

When you are jumping make sure to push with your legs. Bend your legs to jump higher. As you are jumping, and applying force to the ground, the ground will apply a force as well. It will push you up with a normal force. It will apply the same amount of force that you are applying to the ground but in the opposite direction. You apply force to the ground and the ground applies force to you.
 * What Do You Think Now?**

Section 7
12/15/10

In the picture, you see the same girl in two different scenarios. IN the first one, it is easy to pull the shoe because there is ice. There is less friction so the shoe is going with her. In the second scene she is trying to pull the same shoe but on a different surface. She is struggling to pull it over the sand.
 * What Do You See?**

A sports store sells different shoes because they are all useful for different things. SOme sports require special shoes because each shoe and their bottom allows you to do special things. Soccer for example requires cleats because they hold on to the ground as you are running. It helps with balance as well. Rock climbing would require shoes with a rubber bottom making it easier to climb up and grab onto the wall.
 * What Do You Think?**

**Physics Talk** In Newtons second law he says that an object can move at a constant velocity if there is a net force of zero. Friction is a force that keeps things moving without any acceleration. It resists relative motion between and object and a surface, and has to do with something being pulled on a surface. The forces are in opposite directions, making the net force zero. An object being pulled won't travel in a vertical direction, so the vertical force must add up to zero. The upward force (normal force) must be equal to gravity as well. Normal force is perpendicular to the surface or the object's weight. The coefficient of sliding friction is represented by µ. It is the ratio of friction to the normal or perpendicular force. The force of friction is equal and opposite in direction to the force needed to pull an object. Sliding friction has no units because it is a force divided by a force so the units cancel out, it is expressed in decimal form, it changes when the surfaces change, and the perpendicular force is equal to weight, so if the surface isn't flat it will change.

**Checking Up Questions** 1.) You can say that the force pulling the shoe is equal to the friction on the shoe at constant speed because of Newtons second law. It supports this theory that forces must be equal but opposite in direction. The net force must be zero for something to move in at a constant velocity. 2.) The coefficient of friction has no units because a force is being divided by a force, so they cancel each other out. 3.) The coefficient of friction is determined by the ratio of the friction to the normal force.

**Physics To Go** 1.) In soccer when it starts to rain, the floor grass gets more slippery and there is less friction. The ball rolls a lot more and the players tend to slide. The players where cleats though which grip the ground a little better so when it does get slippery, they tend not to fall. 2.) When a person is running track, they don't want to have friction because they want to be able to run as fast as possible. Track runners where lighter shoes so that there isn't as much friction between them and the track. Nothing is slowing them down. 3.) No, you would need to test the friction caused by this surface. Each surface is different though it doesn't look like it. You usually can't tell. 4.) I think they do have shoes for each surface, clay, grass, and hard, because the different surfaces cause different amounts of friction. There sneaker should be the one that causes the right amount of friction for them. 5.) µ= F/N .03= F/ 600 =  18 N  6a.) w= mg  w= (9.8) (1000) W= 9800 N 6b.) µ= f/N  .55= f/9800  Ff= 5390 N  6c.) Fx= ma  -f=ma -5390=1000a a= -5.39 m/s ^2 6d.) Vf= Vi+ at 0= Vi + (-5.39) (6)  32.34 m/s  6e.) The driver was lying. He said that he was driving at 29 meters per second but I calculated that he was traveling 32.34 meters per second.

7.) I think that air resistance and water resistance remain constant if you are running at a constant velocity. I think this because when I am playing sports and I am running outside on a court, I am able to keep a constant and quick speed. It doesn't get harder to run because there is the same air resistance acting on me as I run, but it really all depends on the velocity that you are running at. 8.) The stronger legs you have, the faster you are able to accelerate, but shoes with maximum friction still wont allow you to run as quick as you can even with really strong legs. To reduce friction and accelerate quickly, you can buy shoes with different bottoms in order to help you run quicker. The smoother the bottoms are and the lighter the shoes, the faster you can accelerate. 10.) Friction is important in running because without friction, runners would most likely fall flat on their face. There wouldn't be anything holding them up and they would be sliding around the track. Cleats are good for friction because they allow the player to dig into the ground and allow them keep their balance better. It there is no friction, you wouldn't move. 11.) The runner is about to start racing around the track against his opponent. This should be an easy race for him because he just got brand new shoes that are lighter providing him with good friction but not enough to slow him down. His opponent is wearing heavier basketball sneakers which is slowing him down while he is running. There is a lot more friction and he won't be able to accelerate as fast.

**Physics Plus**

**Lab: Bowling With Blocks** WORK: Percent difference: Class Average- my coeffiecient of friction/ class average (100) = .27- .325 / .325 (100)= 16.92 WORK: acceleration- µ= f/n = .27= f/1.96 F= -.529 -.529= .2a a= -2.56
 * Tension (N) || Ff (N) || Total Weight (N) || µ || Class Average || % difference ||
 * 1.9 for all || 1.9 || 7N || .27 || .325 || 16.92% ||
 * Mass(g) || Mass (kg) || measured time (s) || Measured Distance || Ff (N) || Acceleration (m/s)^2 || Calculated Vi (m/s) || Calculated Time (s) || % error ||
 * 200 || .2 || 1.69 || 4.5 || 1.9 || -2.65 || 4.5 || 1.72 || 11.8 ||
 * 200 || .2 || 1.71 || 5.49 || 1.9 || -2.65 || 9.06 || 3.41 || 49.1 ||
 * 200 || .2 || 1.7 || 4.89 || 1.9 || -2.65 || 9.04 || 3.42 || 50.3 ||

velocity- vf= vi + at 1- 0=vi+ -2.65 (1.69) Vi= 4.5 2- 0= vi+(-2.65) (1.71) vi= 9.06 3- 0= vi + (-2.65)(1.70) vi= 9.04

calculated time: Vf= Vi + at 0=4.5 + (-2.65)t 2- 9.06 + (-2.65)t t= 3.41 3- 9.04 + (-2.65)t t= 3.42

percent error= calculated value- experimental/ calculated (100)

Part III: Questions/ Conclusions 1.) In part one, the coefficient of friction shows the friction over the weight in Newtons. It shows the friction between the wooden block and the ground. 2.) The coefficient of friction I calculated was a little lower than my classmates, but they were very close in number. They will not always be the same because it depends on the correctness, and closeness of measurements, as well as the mass of the individual blocks. When you are measuring and rounding, rounding up or down can make a big difference. 3.) My calculated and measured times were very similar. They were precise, except for one of my measurements which was .03 off. My percent error was very low. 4.) It applies to the real world because we are discussing friction which applies to every moving object in the world. We are talking about forces which exist everywhere. 5.) Experimental errors could be systematic errors when you are calculating the weight in Newtons of the block. If the measuring tape isn't straight, you may calculate the distance wrong, which would affect all the other calculations. The last would deal with timing. If the time was incorrect because of early or late starting of the stop watch, all the calculations would be off.

**What do you think now?** Some sports require special shoes because the shoe will affect how much friction is added. A shoe with a smooth bottom for example wouldn't supply a lot of friction so you would use them on a surface with a lot of friction. In track these shoes would be helpful because the ground isn't as smooth. If you were playing basketball though, the ground is really slippery. You want to wear heavier shoes because they make sure that you don't slip. The coefficient of friction shows how much friction is present when the normal force and friction are applied. On a basketball court for example, you need heavier shoes making the coefficient of friction and the sliding friction higher, making it less likely to slide.

Section 8
**What do you See?** There is a girl who is pole vaulting but before she sticks the stick in the ground she is accelerating. She is running really fast because the faster she goes, the higher that she will go up. Speed changes into height.

If a championship pole vaulter can travel 6 meters with a 5.5 meter pole, they can't necessarily go 12 meters with an 11 meter pole because the pole vaulter may not be accelerating quick enough. They might not be going fast enough to make it over the wall. Speed is a huge factor when you are dealing with how high you can go. I also think that the angle that the vaulter sticks the pole into the ground will affect how high up they will go.
 * What do you Think Now?**

**Investigate** **1/3/10**

Pre-lab: a. We put the edge of the ruler sticking off the table, and put the penny at the edge of the ruler. We applied force to the ruler and when we let go, the penny was blasted into the air. b. The factors that affect it are how far the ruler sticks out, the mass of the coin, the deflection, the position of the penny, and the flexibility of the ruler. 1a.) We will be able to conclude that the farther off the table the ruler is, the higher up the penny will go. We will use the same deflection, and same penny. The less the ruler sticks out, the higher the coin will go 1b.) We will record how high up the penny goes each time we launch it with a meter stick. 1c.) We will use a ruler, a penny, and a meter stick to measure it. The meter stick will measure the height 1d.) We will move the ruler off the table by one inch each time and do 2 trials. We will see how high up the penny goes and compare the height to how far off the ruler is.

Variable tested: How far the ruler sticks out Methods and Materials: a ruler stick, a meter stick and a penny. We will slide the ruler off the table one inch more each time and record how high the penny flies up. DATA: Conclusion: The farther off the table the ruler is, the higher up the penny will go **Physics Talk Summary** The speed and position of an object changes when a force is applied. When the speed and position is changed, the object is able to go back to its original speed and position, some things don't. This concept is the concept of energy. There are two types, kinetic energy and gravitational potential energy. Kinetic deals with motion, and gravitational potential deals with the position of the object, and its vertical launch. The energy changes when a force acts on an object, but the sum of the kinetic energy and potential energy, which is the total energy stays the same. This is why objects are able to go back to their original position and speed. It is because of the law of conservation of energy- energy can't be created or destroyed, and it can be transferred from one form to the other but the total energy stays constant. When a force is applied to an object, with the same or opposite direction for a distance, it is called work. Work is the force multiplied by the distance. When work is done the energy of the object changes. There is also elastic potential energy which is also spring potential energy. It is the energy form a spring because of compression or stretch.
 * How far off the ruler was || 1inch || 2inches || 3inches || 4inches || 5inches ||
 * Trial 1 || 3 cm || 27 cm || 38 cm || 74 cm || 122 ||
 * Trial 2 || 3.2 cm || 29 cm || 44 cm || 84 cm || 128 cm ||
 * Types of Energy || Definition || Equation and Symbol ||
 * Kinetic || Energy of something that has been moving || KE= 1/2(m)v^2 ||
 * Gravitational Potential Energy || Energy something has due to its location relative to the ground (how high it is) || GPE= mgh

(mass x gravity x height) ||
 * Elastic Potential || The energy a spring has when its stretched or compressed || EPE= 1/2kx^2

k is the spring force constant ||
 * WORK || caused when a force is exerted over some distance parallel to the motion || W= f x d

force times distance ||

**Checking Up Questions** 1.) A force needs to act on an object for energy to change. 2.) A penny launched gets its energy from the ruler it was launched from. The ruler has elastic potential energy. 3.) The vaulter needs to get a running start first which gives him kinetic energy which he needs to get high, and catapult. He also needs elastic potential energy from the pole which bends as he is flying. Then he needs potential energy as the pole straightens, and lastly as his height changes, he needs gravitational potential energy to launch him vertically. 4.) The units of all of them are in joules

1/4/11
 * Physics To Go**

1.) As the shot put is sitting in the persons hands, there is gravitational potential energy because it is above the ground. Once it is released, there is kinetic energy as it is increasing speed. When the shot put reaches its highest point, there is gravitational potential energy again because it's velocity is zero, and it is above the ground. There is kinetic as it is falling again and as it hits the ground there is work done by the ground to stop it. 2.) When a golf ball is hit into the air there is kinetic energy. When it reaches it's highest point, there is gravitational potential energy because it isn't moving and about the ground. As it falls back down to the ground there is kinetic energy again, and when it hits the ground there is work. 3.) KE= GPE 1/2 mv^2= mgh  1/2 (12)^2= (9.8)h  72=9.8 h  h= 7.35 meters  4.) The length of the pole doesn't determine the height that a person can jump to because the pole doesn't have anything to do with the energy needed to left the person. Pole vaulting mostly deals with the velocity that the person is running at the start. 5.) The pole's temperature rises while it flexes because the vaulter is using his kinetic energy while running until he sticks the pole into the ground. At this time the energy is being transferred due to the conservation of energy, and this energy makes the poles temperature rise. 6.) KE= GPE 1/2 mv^2= mgh 1/2v^2= (9.8) (4.55) v= 9.44 m/s 7.) Emmas: 1/2 mv^2= mgh  1/2 v^2= (9.8) (4.55)  v=9.44 m/s  Sergei's: KE=GPE  1/2v^2=gh  1/2 v^2= (9.8)(6.14)  v=10.97 m/s  Sergei's speed was 1.53 m/s faster than Emma's which made him go higher up.  8a.) GPE (mgh)= W = KE= 1960 J  KE= 1/2 mv^2 1960= 1/2 (2)v^2 v=44.27 m/s 8b.) You can calculate this without the mass because the masses in Kinetic energy and Gravitational potential energy cancel out. They are equal so therefore you don't need it 9a.) W= EPE F(0.3)= 1/2 kx^2 W= 1/2(1500)(.25)^2 W= 46.875 J 9b.) EPE= KE  1/2 kx^2 =1/2 mv^2  1/2 (1500) (.25)^2= 1/2 (.1)v^2  30.6 J  10a.) EPE=W 1/2 kx^2 =FD 1/2 (315) (.3)^2 = W W=14.2 J  10b.) W=FD  14.2=F(.3)  47.3 J  11.)GPE=EPE mgh=1/2 kx^2 (.04)(9.8)(1)= 1/2 (18) (x)^2 x=.21 J 12a.) F=m  N= kg kg xm/s ^2  12b.) W=fd J=nm 12c.)GPE=mgh kgxm/s^2xm  nxm  J  12d.) KE= 1/2 mv^2

13.) EPE --> KE --> GPE --> KE 14.) KE = W = GPE 15.) THe pitcher throws the ball towards the player, the ball has kinetic energy. The player hits the ball up in the air. It has kinetic energy going up. Once it reaches its highest point, the ball has Gravitational Potential Energy with a velocity of zero. As it falls back down to the earth there is kinetic energy and after hitting the ground, the ground does work. 16.) The soccer ball rolls towards the player it has kinetic energy as it is moving towards him. The player runs in the direction of the ball and uses energy in order to do work. He kicks the ball up in the air. The ball now has gravitational potential energy as it is rising up. The ball then falls back down to the ground and into the goal

This is because it is the speed that you are running at before you pole vault which defends how far you can go. This is because the kinetic energy you are using in order to run must be equal to the Gravitational Potential energy which decides how high you can go. The law of conservation of energy states this, that the energy can't be created or destroyed. It is equal. Pole vaulting is depended on speed, the flexibility of the pole, and the height of the person running.
 * What do you Think Now?**

Section 9
1/6/11

An ice skater has jumped up pretty high because they are by a helicopter. The skater seems to be twirling in the air which means that he would have to be there for some time. It seems like they are defying the law of gravity because they have a long hang time in the air.
 * What do you see?**

The hang time of some athletes seems to defy the law of gravity because some athletes are able to stay in the air for a longer time then possible. Gravity seems to act on them slower. I think that a figure skater does have to defy the law of gravity to stay in the air to land a triple axel because it takes them longer to land on the ground.
 * What do you Think?**

Pre-lab: 2.) The skater was in the air for 20 frames. 3.) 1/30 second (20 frames) = 2/3 second 4.) During the middle frames the skater seemed to hang in the air. During frames 5-8 the skater seemed to hang in the air defying gravity. 5a.) The player was in the air for 31 frames 5b.) 31(1/30) = 31/30 seconds.. about 1 second 5c.) The basketball player was in the air for a longer time than usual. His hang time in the air seemed to defy gravity.
 * Investigate**

1.) first you bend your knees, and then you unbend your knees but you are still on the floor. Work is involved because you are causing work on the floor. You are pushing off the floor. Then your in the air for some amount of time, and you go up a certain height off the floor. As you are going up you are using kinetic energy. When you reach the highest point, there is gravitational potential energy. 2a.) We will be able to conclude that the more force that you use, the higher up you will go. 2b.) We will record the height that you are in the air and we will need to know our mass in newtons. 2c.) We will use a meter stick to measure out height 2d.) Our data will be in a chart made in data studios. This graph will compare the force in our jump from pushing off the ground to the time that we are in the air. 4.) My force calculated: W= GPE FD=mgh f(.05)= (48.5)(.15)(9.8) F= 1425.9 Netwons My force on scale: 983.53 5.) My calculations were far off from my calculations on the scale. There was a 31.02% error % error= 1 calc-exp/ calc x 100  % error= 1425.9-983.53/ 1425.9 x100  % error= 31.02

Peak position is where there is gravitational potential energy. When you are about to jump and your knees are bent you have elastic potential energy. Although there is no spring, the chemicals in your muscles provide the potential energy. This energy changes to kinetic energy when you are jumping. To show energy transformations, you can use a table. All energies must be equal. A person who can jump higher has more gravitational potential energy and a higher peak point. A table can be used to show the amounts of each type of energy. It would show the position and then each type of energy and how many joules you are using for each. The total energy must be conserved. If you are jumping on a trampoline instead of a hard floor, your kinetic energy coming down would change to elastic potential energy because of the springs when you are coming back up. There are many different energies that deal with heat as well like nuclear energy or light energy for example. They also follow the conservation of energies where they can't be created or destroyed, only equal. A specific object can lose or gain energy but the whole system must keep equal energy.
 * Physics Talk**

1.) It comes from elastic potential energy when you are bending your knees. The energy comes from chemicals in your muscles. 2.) In the launch position and at the peak of your jump, the person will have gravitational potential energy. As they are jumping up though there will be kinetic energy. This will turn into gravitational potential energy. 3.) Nuclear energy, sound energy, and light energy are all different types. They are energies due to heat.
 * Checking Up Questions**

1/9/11
 * Physics to Go**

1.) W= GPE FD= mgh  W=50 (9.8)(1)  W= 490 J  2.) W + GPE ---> Kinetic energy --> Work 3.) In order to test this we would watch the video like we did in class in slow motion scene by scene. We would check to see if the player moves in a parabola like form which means that he is not hanging in the air. 4.) Although it may seem like the laws of gravity can be defied when doing sports like ice skating, it is not true. The person might have evidence that seems to be true but it is not. The arguing person could explain that it looks like they are defying gravity because of how small their displacement is. 5.) A person can increase their vertical jump by bending their knees farther down which increases their elastic potential energy and by decreasing your mass. 6a.)W=FD W=1(1)= 1 J 6b.) W=FD  W= 1 (10)= 10 J  6c.) W= 10 (1) W= 10 J 6d.) W= FD  W= .10 (100)  W= 10 J  6e.) W=FD W= 100 (.10) W= 10 J 7a.) GPE= 1 J  7b.) GPE= 10 J  7c.) GPE= 10 J  7d.) GPE= 10 J  7e.) GPE= 10 J  8a.) KE= 1 J  8b.) KE= 10 J  8c.)KE= 10 J  8d.) KE= 10 J  8e.)KE= 10 J  9.)W= FD  W= (50) (43)  W= 2150 J  10.) KE= 1/2mv^2 KE= 1/2 62(8.2)^2 KE= 2084.4 J 11a.) a= f/m  a= 30/5  a= 6 m/s^2  11b.) W=Fd W=30 (18.75) W= 562.5 J 12a.)W= FD  40,000=3200 N (d)  D= 12.5 meters  12b.) a=f/m a= 3200/1200 a= 2.7 m/s^2 13.) KE--> W KE= W  1/2 mv^2= FD  1/2 (.150) (40)^2= W  120 J= W  14.) W= KE  FD= 1/2 mv^2 417d= 1/2 (64) (15)^2 417d=7200 d=17.27 meters 15.)
 * || KE || GPE || EPE || Sum ||
 * Running || 100 J || 0 || 0 || 100 J ||
 * Full Bend of pole || 10 J || 0 || 90 || 100J ||
 * Peak Height || 0 || 100 J || 0 || 100 J ||
 * Landing || 40 J || 60 J || 0 || 100J ||
 * Cushion Collapse || 0 || 0 || 0 || 0 ||

16.) 17.)  18.) The basketball player is about to take a shot. He dribbles down the court at full speed. He has kinetic energy. He then jumps up in the air in a parabola like form. He is able to jump really high and far because of the amount of kinetic energy he had. At the highest point, he has gravitational potential energy. He then shoots the ball and falls back down to the ground with kinetic energy.
 * || KE || GPE || EPE || Sum ||
 * Peak Height || 0 || 1000 J || 0 || 1,000 J ||
 * Landing || 100 J || 400 J || 500 J || 1,000 J ||
 * Lowest height || 0 || 0 || 1,000 J || 1,000 J ||
 * || KE || GPE || EPE || Sum ||
 * Top of Mountain || 0 || 1,000 || 0 || 1,000 ||
 * Middle of Mountain || 500 J || 500 J || 0 || 1,000 J ||
 * Bottom of Mountain || 1,000 J || 0 || 0 || 1,000 J ||

**Active Physics Plus** 1/10/11

1a.) GPE= GPE +KE mgh= 1/2 mv^2 +mgh  9.8(50)=1/2 v^2 +(9.8)(30)  490=1/2V^2+294  v= 19.8 m/s  1b.) It is advantageous that the mass is independent because when you are finding the velocity, the mass cancels out. Because it is independent, you don't need to know the mass. 2.)GPE+EPE=KE mgh +1/2kx^2= 1/2mv^2  .3(9.8) (2) +1/2 (60)(.4)^2= 1/2 (.3)v^2  10.68=.15v^2  v=8.4 m/s  3.) GPE+W=GPE+KE+W mgh+FD=mgh+FD+ 1/2mv^2 200(9.8)(25) +200,000=1/2(200)(9.8)h+50,000 249000=210000+1960h h=19.9 meters

**What do you Think Now?**

Although it looks like some athletes defy gravity when they jump, they don't. It is impossible to defy gravity. It looks like this though because when a player jumps into the air, there is little displacement each time. They player goes up slowly. If you were to watch them in different frames, or in slow motion, you would see the player moving up and then down very slightly each time. A figure skater doesn't defy gravity when doing a triple axel, they just have enough kinetic energy to stay in the air longer. They use the conservation of energy because they know that the more kinetic energy they have, the longer they will be able to stay in the air because this energy is converted into gravitational potential energy. They rise slowly making them look like they are in the air longer.