Chapter+3

Shana Smolinsky's Wikilog - Period 6 CP Physics - E. Burns - 2011 toc

Section 1
1/18/19

**Accidents and Safety Article HW** Article Title: Women injured in Two Car Accident Date of Article: 1/7/11

In this article a woman was driving on an icy road. She lost control of her car and it slid quickly on the ice. Because she was driving to fast, the car flipped over and flipped back upwards. It finally stopped when in landed in the ditch. Luckily she wasn't injured but she was still admitted into a hospital. Her car slid of the road but she was safe. []

The car is crashing into a barrier. The front of the car has dented in. The air bag came out and the driver is going forward into the air bag. The airbag is protecting the driver from going through the window. If it wasn't there the driver would go straight through because he is still moving even though the car stopped.
 * What Do You See?**

If a serious accident were to occur I could protect myself with some sort of padding. If I was on a bicycle for example, I would wear a helmet to protect my head. An airbag in a car would protect me as well for holding me back in my seat. My seatbelt would do the same which is why it is important to wear it.
 * What do you Think?**

1/19/11
 * Investigate**

1.) 2.) I am a Novice Analysts 3.) (yes/no) || New Cars  (1,2,3) ||
 * Safety features || Means of protection || Pre-1960 cars
 * seat belts || Keep person from going through window. It holds you back from going forward, and stops you from moving after the car stops. || no || 1 ||
 * head restraints || Keeps neck from breaking. Keeps head from flying back. Prevents whiplash || no || 1 ||
 * front airbags || It provides cushioning in collision when moving forward || no || 1 ||
 * back up sensing system || It keeps you from hitting something in back of you when reversing. helps see your blind spots || no || 3 ||
 * front crumple zones || Increases the time that the collision occurs || no || 2 ||
 * rear crumple zones || increases the time that the collision occurs || yes || 2 ||
 * side-impact beams in doors || It protects the doors because they are made of aluminum making the car harder to crush || no || 2 ||
 * shoulder belts for all seats || Makes sure the upper body is protected from jolting forward. Keeps people in seats || no || 1 ||
 * anti-lock braking systems (ABS) || Creates friction to stop in bad weather || no || 2 ||
 * tempered shatterproof glass || It is tougher glass so it doesn't break as much. It prevents cuts || no || 1 ||
 * side airbags || Protects head an torso || no || 2 ||
 * turn signals || It prevents collisions by warning the person in back of you where you are turning. || yes || 1 ||
 * electronic stability control || It helps protect you from rollovers || no || 2,3 ||
 * energy-absorbing collapsible steering column || Prevents chest trauma || no || 1 ||

Accidents occur a lot so vehicles are made in order to avoid them. Engineers make it safer for the driver as well as a pedestrian if they are hit. This started when people noticed the danger of driving without certain things like seat belts. Some people get into accidents now because they think that they are safer because of their car. A person with four wheel drive might drive more recklessly for example resulting in an accident.
 * Physics Talk**

1.) Vehicles are now safer because they have seat belts to keep people in their seats, they have anti lock brakes to prevent people from skidding in bad accidents, and they fixed the dashboard and added airbags to protect a person in collision. They are now cushioned to prevent injury. 2.) The four wheel drive, because people are now driving more carelessly and the increase of distance driven results in accidents.
 * Checking Up Questions**

1.)seat belts- F and R head restraints- F and R  front airbags- F  backing up system- R  front crumple zones- F  rear crumple zones- R  side impact beams-S  shoulder belts- F and R  anti-lock braking systems- F  tempered shatter proof glasses- F S and R  side airbags- S  turn signals-R  electronic stability control- T  energy- absorbing collapsible steering column- F  2.) In bicycling you can use a helmet, knee and elbow pads, working brakes, wrist pads, and a bell. 3.) For inline skating you can use a helmet, and knee, wrist and elbow pads. 4.) Knee,wrist and elbow pads, and a helmet
 * Physics To Go**

You can protect yourself from injury by making sure your car is equipped with things like airbags, seat belts, four wheel drive, turning signals and other things that help you in times of a crash. Padding and helmets may also help when you are on different forms of transportation other then an automobile. In an accident if you aren't wearing your seat belt or proper padding, it won't help you it will only injure you more.
 * What do you think Now?**

Section 2
**Investigate X2: Newton's First Law and Seatbelts** 1/31/11

** Objectives: ** ** 1.) What happens to a passenger involved in a car accident without and with a seatbelt? ** Without a seat belt, the passenger would be pushed forward into the front window. They could get seriously injured because of the collision. With a seatbelt, the passenger would be held in his seat because it would stop them from moving forward into the windshield.  2.) What factors affect the passenger's safety after a collision? A passenger's safety after a collision is affected by the seatbelt that they are wearing before. If they are being held back in their seat, they are hopefully only harmed slightly. 3.) How would a seat belt for a race car be different from one available on a regular car? A seat belt for a race car must be stronger than a regular car because a race car goes a lot faster and therefore, when the car collides, the person will go forward more. The seatbelt must hold them in place.

Hypothesis: Respond to each of the above objectives fully.

Materials: List any materials used and draw a labeled diagram of your set-up (alternatively, include a snapshot or video).
 * Clay
 * Ramp and cart
 * Ribbon/ string/ thread/ yarn/ tape
 * Picture of before and after


 * Procedure: **


 * 1) Make a clay figure and then place the figure in the cart.
 * 2) Arrange a ramp so that the endstop is at the bottom of the ramp.
 * 3) Adjust the height of the ramp to make a very shallow incline.
 * 4) Send the cart down the ramp.
 * 5) Very gradually increase the height of the ramp until significant “injury” happens to your figure. Make a note of this height.
 * 6) Fix your clay figure. Create a seatbelt for the figure and take a "Before" picture and post in your data table.
 * 7) Send your cart and passenger down the ramp at the same height as in Step 5. Be sure to record your observations specifically and carefully. Take an "After" picture and post in your data table to supplement your written observations.
 * 8) Repeat Steps 6 and 7, using different types of material for the seatbelt.

Data and observations: Injury Height with no seatbelt: ﻿ .20 m through his body and sliced his neck.
 * Type of Seatbelt || Before Picture || After Picture || Description and Observations || Group ||
 * Thread || [[image:activephysics-pvrhsd:111Photo_45.jpg width="255" height="191" caption="111Photo_45.jpg"]] || [[image:activephysics-pvrhsd:111Photo_46.jpg width="256" height="192" caption="111Photo_46.jpg"]] || Arm chopped off. The seat belt cut

Group 6 ||
 * Wire || [[image:proringer:hershey_kissboybefore.jpg height="192" caption="hershey_kissboybefore.jpg"]] || [[image:proringer:hersheykissafter.jpg height="189" caption="hersheykissafter.jpg"]] || The wire was put around the passenger pretty tightly in order for him to stay on the cart after the collision. The wire was so tight that it sliced his arms and chest. The wire material is not a good idea because it can harm the person even if the collision wasnt that bad. || 1 ||
 * String || [[image:activephysics-pvrhsd:stringgPhoto_86.jpg width="255" height="191" caption="stringgPhoto_86.jpg"]] || [[image:activephysics-pvrhsd:strringgPhoto_87.jpg width="256" height="192" caption="strringgPhoto_87.jpg"]] || Our seatbelt made of string went around the chest. After going down the ramp, our passenger was still in the cart without any injuries. || 2 ||
 * Yarn || [[image:activephysics-pvrhsd:sgrant22221.jpg width="256" height="192" caption="sgrant22221.jpg"]] || [[image:activephysics-pvrhsd:sgrant11.jpg width="256" height="192" caption="sgrant11.jpg"]] || Our observation of the yarn seat belt is that when the accident occurred, the figure slammed forward. This shows that the yarn is not sturdy enough to prevent an injury in an accident. || 5 ||
 * Ribbon || [[image:activephysics-pvrhsd:Photo_38lp.jpg width="255" height="191" caption="Photo_38lp.jpg"]] || [[image:activephysics-pvrhsd:Photo_41lp.jpg width="256" height="192" caption="Photo_41lp.jpg"]] || We made a seatbelt out of ribbon that went around his waist shoulders and chest. When the cart went down the ramp, the seatbelt held him in place and the clay person didn't leave the cart. || 3 ||
 * 1- in masking Tape || [[image:activephysics-pvrhsd:Photo_7758.jpg width="256" height="192" caption="Photo_7758.jpg"]] || [[image:activephysics-pvrhsd:Photo_7662.jpg width="256" height="192" caption="Photo_7662.jpg"]] || we took a piece of tape and folded it over so there was no sticky part. We then twirled the end to make tying it easier. We put the tape belt around "her" waist and tied it around the bottom of the cart. Despite my face in the after picture, the tape actually worked well because our figure was unharmed and barely moved. || 4 ||


 * 1) Define the terms: inertia, force and pressure. Inertia states that an object in motion stays in constant motion unless acted on by a force, and an object at rest will stay at rest until acted on by an unbalanced force. A force is an interaction between two objects that results in the acceleration of one or both of the objects. Pressure is the force per area where the force is perpendicular to the surface; it can be measured in N/m squared or pascals.
 * 2) In the collision, the car stops abruptly. What happens to the “passenger”? The passenger is still moving at the speed that the car was originally moving at so in a collision the person is keeps moving forward until a force, like a seatbelt or the front window stops them. The person jolts forward.
 * 3) What parts of your passenger were in greatest danger (most damaged)? The passenger's head is in great damage because if they aren't wearing a seat belt, they might hit their head on the window and cause serious damage. Wearing a seat belt will help prevent this.
 * 4) What does Newton’s first law have to do with this? Newton's first law of inertia relates to this because seat belt is the force that is acting on the moving object (the person).
 * 5) What materials were most effective as seatbelts? Why? Wider materials are more effective for a seat belt. Materials that spread out the force making less pressure is safer which is why ribbon can be a better seat belt than wire.
 * 6) Use Newton's first law of motion to describe the three collisions. In the first collision the pole and the automobile are exerting the same force on each other. Because the force of the pole was stronger than the force of the automobile, it caused the car to decelerate and stop because of inertia. In the second collision inertia is present because a person in the car after the collision keeps traveling forward but a force in the car exerts force on them which makes them stop. They both exert forces on each other (the car and the person). In the third scenario, the person's body is acting as a wall. The person's organs keep moving forward until they are acted on by the force of the body. This demonstrates inertia.
 * 7) Why does a broad band of material work better as a seatbelt than a narrow wire? A broader band of material allows the force to be spread out when a person is in a collision. A narrow wire for a seatbelt allows all the pressure to be in one small area because it is smaller and thinner. This makes the broad band more safe because it is more firm.

Conclusion:
 * 1) · Using Newton's First law of Motion, explain why a seat belt is an important safety feature in a vehicle. What factors affect the effectiveness of a seatbelt? What would you need to consider when designing a seatbelt for a race car? Use specific observations from this investigation to support your answers to these questions. A seat belt is one of the most important safety features in a car because when the car collides and stops moving, the passenger continues to move forward at the same velocity. They will keep moving forward until a force acts on them. The seat belt applies the force so that they won't go through the windshield. The factors that affect a seat belt is the broadness of thickness of it. The broader it is, the more spread out the pressure will be throughout the passengers body. In a race car, the seat belt needs to be really broad because they are moving really quickly and so their needs to be a lot of force holding them back, and the pressure needs to be distributed equally to their body. It must also be thick.
 * 2) · Explain at least 1 cause of experimental error. Be sure you describe a specific reason. One experimental error would be if we didn't test all the different materials to see if they all protected the person. For example if we only did one experiment testing the ribbon as a seat belt, we would have concluded that a seat belt will always protect the passenger but after experiments, we concluded that wire wouldn't protect the passenger. This means that seat belts need to be tested for effectiveness and not all materials will keep a person safe.
 * 3) · How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?) To improve this lab I would use more materials to test to compare the similarities between the effective materials. I might even use a thinner ribbon and see which one was more effective. I could also test the experiment from different heights on the incline and see which caused more injury.

Section 3
Investigate X3: Energy and Air Bags


 * Objective:**
 * How does an air bag protect you during an accident? An airbag protects you because it holds you in your seat from the front. It pushes against you with enough force to stop you from moving.


 * Hypothesis:** Respond to the objective fully.


 * Materials:** List any materials used and draw a labeled diagram of your set-up (alternatively, include a snapshot or video).


 * Procedure:**

**Note: //You may want to use the available technology to take "Before" and "After" pics to post in your data table to assist and elaborate on your written descriptions.//**

// 1. Measure the height of your egg #1. // // 2. Place an egg in a ziplock bag, squeezing out all of the air in the bag before sealing. // // 3. Hold a ruler up on the table vertically. Hold the egg vertically at the 2 cm mark. (Keep the excess bag on top.) Drop it. Record your observations. // // 4. Hold the egg the same exact way at the 4-cm mark and repeat. Continue this process until the egg shell is slightly cracked. // // 5. Continue until the egg is smashed and the yolk leaks out. Measure the amount of egg still undamaged. How much of the egg is smashed? Be sure to record detailed observations. // // 6. Fill a bowl with rice and place the bowl inside of the box lid. // // 7. Measure the height of your egg #2. // // 8. Drop the egg from the smash height (Step 3). Measure the amount of egg sticking up out of the rice bed. How much of the egg is buried in the rice? Also, record your observations. // // 9. Repeat this, increasing the height in 2-cm increments until the egg is cracked, and then smashed. //

//**Data and observations:** Add more columns/row as needed.// Mass: .5638 kg height: .055 m || 2 cm || slight crack || There is one small crack ||  || mass: .05757 kg height: .056 m || .28 m || no crack || .027 meter indent (no damage) || .027 m ||
 * **Egg #** || **Drop Height** || **Cracked or Smashed?** || **Description and Observations** || Dented flour ||
 * 1
 * 1 || .04 m || cracked || The crack got bigger ||  ||
 * 1 || .06 m || cracked || The bottom of the egg is cracked and dented but no yolk ||  ||
 * 1 || .08 m || crack || The crack spread out and there are more ||  ||
 * 1 || .10 m || cracked || The crack got bigger but still hasn't been smashed ||  ||
 * 1 || .12 m || Cracked || The egg shell is starting to break off ||  ||
 * 1 || .14 m || cracked || The egg shell cracked more ||  ||
 * 1 || .16 m || cracked || The egg shell cracked more ||  ||
 * 1 || .18 m || cracked || more cracks and more pieces of shell fell off ||  ||
 * 1 || .20 m || cracked || the egg shell cracked more ||  ||
 * 1 || .22 m || cracked || The egg shell keeps cracking ||  ||
 * 1 || .24 m || Cracked || The egg shell split in half completely and the white part came out. ||  ||
 * 1 || .26 m || cracked || The yolk is still in tact in the egg ||  ||
 * 1 || .28 m || smashed || The yolk is out ||  ||
 * 2
 * 2 || .30 m || no crack || no damage || .02 m ||
 * 2 || .32 m || no crack || no damage || .024 m ||
 * 2 || .34 m || no crack || no damage || .025 m ||
 * 2 || .36 m || no crack || no damage || .026 m ||
 * 2 || .40 m || no crack || no damage || .027 m ||
 * 2 || .44 m || no crack || no damage || .035 m ||
 * 2 || .48 m || no crack || no damage || .038 m ||
 * 2 || .52 m || no crack || no damage || .039 m ||
 * 2 || .56 m || no crack || no damage || .04 m ||
 * 2 || .60 m || no crack || no damage || .04 m ||
 * 2 || .66 m || no crack || no damage || .04 m ||
 * 2 || .72 m || no crack || no damage || .041 m ||
 * 2 || 1 ||  ||   || .042 m ||


 * Calculations:** Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results.
 * What is the gravitational potential energy in each trial?
 * How much work is done in each trial?
 * How much force was used to stop the egg in each case of steps 5, 8 and 9.

** *Read the Physics Talk p279 - 287 before answering the following questions. * ** 1. This investigate is an analogy for a person in an automobile collision. What does the egg represent? What does the table represent? What does the rice represent? The egg represents the person in the car accident. When the egg breaks it represents the person getting hurt. The table represents the object that the car is crashing into and the rice or flour represents the airbag protecting the person 2. Define the terms: Kinetic Energy and Work. Kinetic energy is the energy the object has when it is moving. It is determined by the objects mass and velocity. Work is the amount of force applied on an object over a certain distance. 3. What factors determine an object's kinetic energy? Velocity and mass determine the kinetic energy. When work is done on an object, what is the effect on the object's kinetic energy? It can either decrease or increase the objects kinetic energy depending on the direction of the object and the distance the object moves. 4. How does the force needed to stop a moving object depend on the distance the force acts? The work needed to stop an automobile is fixed depending on its velocity because it must match the kinetic energy, so if the distance is larger the force is most likely smaller and if the distance is smaller the force is probably larger. 5. What difference does a soft landing area make on a passenger during a collision? A soft area landing makes a passenger safer during a collision because it protects their body and head with cushion. 6. How does a cushion reduce the force needed to stop a passenger? When a cushion like an airbag strikes a person, they traveler a larger stopping distance and therefore, less force is needed to stop them. 7. What does the law of conservation of energy have to do with this? This applies to the conservation of energy because the law states that energy can not be created or destroyed, and this deals with how kinetic energy is turned into work when a person or automobile in a crash stops moving. The person for example is moving which is kinetic energy but the airbag is the force that holds them back. These two types of energy are always going to be equal according to the law of conservation of energy.
 * Questions:**

1.) Using the law of conservation of energy, explain how an air bag can protect you during an accident. Use specific observations from this investigation to support your answers to these questions. The airbag is used to protect a person in a collision. It is supposed to hold the person back because when there is a collision, they will continue to move forward until a force (the airbag) acts on him. The law of conservation of energy says that the kinetic energy can't be destroyed, it must be transferred into the form of work. The force of work is the airbag.
 * Conclusion:**

2.) Explain at least 1 cause of experimental error. Be sure you describe a specific reason. One experimental error in this lab could have been if we dropped the egg at the wrong distance. If we dropped it from a couple centimeters up, our calculations would be wrong.

3.) How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?) To improve this lab I would probably have tested dropping the egg from the same distance several times to see if i measured the indentation in the flour right. I would probably also use a smaller ruler rather than a meter stick to measure the indent in the flour because it might be easier to read.

Section 5

 * Momentum- quantity of motion descrived by the product of mass and velocity
 * p=mv
 * large mass and small velocity
 * small mass and large velocity
 * large mass and large velocity

**Physics To Go** 11/9/11

1.) The automobile that is stopped has a lot less momentum because it isn't moving even though they have the same mass. The automobile that isn't moving will move at the same speed in the opposite direction they were hit in because the momentum is transferred. The other car that hit it will stop moving. 4.) They want their defensive and offensive linemen to weigh about 140 kg because they want them to have a lot of mass so hopefully they will have more momentum than the person on the other team. It helps them tackle better because they can defeat the other team. 5.) The vehicle that gets knocked backwards depends on the mass and velocity. The one who's mass and velocity multiplied together has more momentum and will knock the other car backwards. 6.) p= mv  p= 10(1000) P= 10000 10000= 10000v v= 1 m/s

Investigate X6: Momentum and Inelastic Collisions

Objective: What physics principles do the traffic-accident investigators use to "reconstruct" the accident?

Materials: List any materials used and draw a labeled diagram of your set-up (alternatively, include a snapshot or video).

Procedure:
 * 1) Place a motion detector at the right end of a track. Open up data studio. Dump "Velocity" into "Graph" display, and enlarge this.
 * 2) Place a cart on the middle of the track with the velcro to the right. Call this the "target cart." Place a second identical cart on the right end of the track. Call this the "Bullet cart".
 * 3) Click "Start" on Data Studio, and then push the bullet cart very gently towards the target cart so that they collide and stick together. You may need to practice this a few times. Be sure to get your body out of the way of the motion detector!
 * 4) Examine the graph produced by the motion detector. Using the Smart Tool, find the velocity right before and right after the collision. Record this in your data table.
 * 5) Vary the masses of the carts and repeat the process 5 times.

//**Data and observations:** Add more columns/row as needed.//
 * **Mass of Bullet Cart (kg)** || **Mass of Target Cart (kg)** || **Speed of Bullet Cart**(m/s) || **Speed of Target cart (m/s)** || **Combined masses (kg)** || **Final Velocity of both carts (m/s)** ||
 * .501 || .499 || .85 || 0 || 1.009 || .42 ||
 * .726 || .499 || .84 || 0 || 1.225 || .49 ||
 * 1 || .499 || .65 || 0 || 1.499 || .5 ||
 * 1.25 || .499 || .79 || 0 || 1.749 || .61 ||
 * 1.5 || 1 || .75 || 0 || 2.5 || .45 ||
 * 1 || 2 || .76 || 0 || 3 || .31 ||

1.) Find the initial momentum of the bullet cart for each trial. p= mv 1- p= (.501)(.85)= 0.426 km(m/s)  2- p= (.726)(.84)=0.609 km(m/s)  3- p= (1)(.65)=0.65 km(m/s)  4- p= (1.25)(.79)=0.988 km(m/s)  5- p= (1.5)(.75)= 1.125 km(m/s)  6- p= (1)(.76)= .76 km(m/s) 2.) Find the initial momentum of the target cart for each trial. p=mv 1- p=(.499)(0)= 0 km(m/s) 2- p=(.499)(0)= 0 km(m/s) 3- p=(.499)(0)=0 km(m/s) 4- p=(.499)(0)= 0 km(m/s) 5- p=1(0)=0 km(m/s) 6- p=2(0)=0 km(m/s) 3.) Find the sum of the initial momenta of the two carts for each trial. 1- 0.426+0= .426 km(m/s) 2- .609+0= .609 km(m/s)  3- .65+0= .65 km(m/s)  4- .988+0= .988 km(m/s)  5- 1.125+0= 1.125 km(m/s)  6- .76+0= .76 km(m/s) 4.) Find the final momentum of the combined carts for each trial. p=mv 1- p= (1.009)(.42)= 0.424 km(m/s) 2- p= (1.225)(.49)= 0.6002 km(m/s) 3- p= (1.499)(.5)= 0.7495 km(m/s) 4- p= (1.749)(.61)= 1.0669 km(m/s) 5- p= (2.5)(.45)= 1.125 km(m/s) 6- p= (3)(.31)= 0.93 km(m/s)
 * Calculations:** Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results.

** *Read the Physics Talk p312 - 315 before answering the following questions. * ** 1.) Compare the initial momenta (calc 3) to the final momentum (calc 4). (Allow for minor variations due to uncertainties of measurement.) The momentum from the initial momentum compared the the final momentum were generally the same, though each were off by a couple numbers in the decimal. Even so, the numbers were all precise when they were compared. 2.) List the 6 types of collisions (top of page 312) and a brief description. The first type of collision is when an object hits another object that isn't moving, and the two stick together and start moving at the same speed. The second is when two unmoving carts explode from a spring in between them making them travel in opposite directions. The third is when one moving object hits and unmoving object, the one that was moving stops and the unmoving one starts to move in the opposite direction The fourth is when a moving object hits one that isn't moving and they both start moving at different speeds. The fifth is when two moving objects hit each other and they both go off and move at different speeds. The sixth is when two moving objects hit each other and stick together and move off at the same speed. 3.) Which types of collisions are definitely inelastic? How do you know? The collisions that occur when two carts stick together are inelastic like collision one. Explosion collisions are also inelastic. You know they are elastic because they stick together after a collision. 4.) Which types of collisions are definitely elastic? How do you know? Collisions are elastic when the two cars bounce apart, like the second collision. You know they are elastic when kinetic energy is conserved and the carts end up moving in different directions. 5.) Define the law of conservation of momentum. It states that the total momentum when a collision occurs must be equal to the amount of momentum after the collision if no other forces are acting on the system. 6.) Use the law of conservation of momentum to describe what happens when a cue ball hits the 15 balls in the middle of the pool table. The momentum that you use to strike the cue ball will be transferred to the momentum that the balls are hit, so the momentum will always remain the same.
 * Questions:**

· Based on the law of conservation of momentum, how can the traffic-accident investigators use to "reconstruct" the accident? What does it mean to "conserve" momentum? They use the law of conservation of momentum to find out how fast the two cars were going and who was speeding because the momentum has to remain equal throughout.
 * Conclusion:**

· Explain at least 1 cause of experimental error. Be sure you describe a specific reason. One experimental error would be if we didn't measure the mass right. If we didn't weigh the object correctly than the momentum of the cars would be different because it is depended on mass. · How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?) I would improve this lab by testing more trials and using a larger mass to put on top each time to make sure that my calculations were correct.

2/13/11
 * Physics to Go**

2) __x ---> <---x__ 2a.) vehicle 1: p=mv p= (1)(2) p= 2 km(m/s) Vehicle 2: p= -2 km(m/s)

b. mvi+m2vi2=p before 1kg(2m/s)+1kg(-2m/s) 0= p 0 is the total momentum c. mvi+m2vi2=mvf+m2vf2 1kg(2m/s)+1kg(-2m/s)= 1kg(vf)+1kg(vf2) 0=2kg(vf) 0=v total momentum is 0 3. masses are all equal / vi=? Vif= 4m/s........ Vi2= 0/ V2f= 4 m/s mvi+m2vi2=mvf+m2vf2 mvi+mvi=m(4)+m(4) Vi= 8m vi=8 m/s 5. After they collide, B gains the 4000 kh(m/s) (momentum) that A transferred to it. The change in momentum is 0 because of the transfer of momentum. 6. mvi+m2vi2=mvf+m2vf 2000(3)+2000(2)=2000vf+2000vf 10,000=4000vf 2.5m/s=Vf 7. mvi+m2vi2=mvf+m2vf2 80(10)+100(8)= 80vf+100(9.78) 1600=80vf-978 622=80 Vf 7.8m/s= Vf  8. __X---> <---X__ mvi+m2vi2=mvf+m2vf2 3(2)+1(-2)=3(0)+1vf 6-2= 1Vf It moves at 4m/s=Vf 9.) mvi + mvi = m2vf2 + m2vf2 45 (0) + 75 (0) = 45(-2) + 75(vf)  0= -90 +75 vf  90= 75vf  **vf= 1.2 m/s**  10.) mvi + mvi = m2vf2 + m2vf2 .35(20) + .060 (-30) = .35(10) + .060vf 7 - 1.8 = 3.5 +.060 vf 5.2= 3.5+ .060vf **vf= 28.3 m/s** 11.) mvi + mvi = m2vf2 + m2vf2 3(0) + 1(4) = 3(2)+(1) vf  0+ 4= 6+vf  **-2= vf**  12.) 90(0) + .16(30) = 90vf+.16vf 4.8=90.16vf **vf= .05 m/s** 13.) mvi + mvi = m2vf2 + m2vf2 45 (1.10) + .08(0)= 45vf+.08vf  49.5=45.08 vf  **vf=1.09 m/s**  14.) mvi + mvi = m2vf2 + m2vf2 1700 (10) +m(-25)= 1700(-5)+ m(-3.75) 17,000- 25m= -8500 -3.75m 25500=21.25m **mass of B= 1200 kg**

Section 7
2/15/11
 * PTG**

4.) You need to bend your knees when you jump on the ground because it gives you a larger distance to fall on the ground. As you are landing you are applying force to the ground and the ground is applying the same amount of force back. When you are bending your knees, the force decreases because the distance increases making it less painful. 6a.) change in momentum= final- original (1200)(0) - 1200(10)= 0 - 12000 -12000 km(m/s) 6b.) change in momentum= final- original 1200(5) - 1200(10) = 6000-12000  -6000 km(m/s)  7.) FT= m delta v  10000 (1.2) = impulse impulse= 12,000 12,000= (1200) (v) change in velocity= 10 m/s 8.) FT= m delta v F(.1) = (1500)(-5)  F= -75000 N  10.) In the first graph, a collision is exerting a lot of force over a shorter period of time. The person driving is most likely injured or killed because of the force of the impact. It isnt safe at all. In the second collision, there wasnt a lot of force exerted over a little time, so the collision was probably safer.