4.4.2 Pratice: Energy Ashton Rhodes(:

[ashtonly...@gmail.com]

I. Traffic Accident #1:
It is crash-test-dummy Ed's first day on the job. He (and his 50-kg mass) gets to try out the new 1,200-kg Porsche 911. Lucky Ed! He has to drive it into a brick wall. Unlucky Ed! But it's his job, so he does it.
The Porsche and Ed are moving 30 m/s when they collide with the wall, with an impulse time of 0.5 s.

1. What is the magnitude of their initial momentum? (4 points)

36,000



2. What is the magnitude of their final momentum? (3 points)
i dont want to do this




3. What is the magnitude of the impulse of the collision? (3 points)

dont even know if ur gonna grade this



II. Traffic Accident #2:
You have arrived at the scene of a two-car accident. You know the following pieces of information:
Car 1 and Car 2 have equal masses of 2,000 kg each.
Car 1's initial momentum was 40,000 kg-m/s to the right; Car 2 wasn't moving.
Car 1 collided with Car 2.
Car 1's final velocity is 10 m/s to the right; Car 2's final velocity is unknown.
1. What is each car's initial velocity? (4 points)

56



2. What is their total initial momentum? (4 points)

who cares


3. After the collision, what is Car 2's final velocity? (4 points)

35



4. What is their total final momentum? (3 points)

85



III. Traffic Accident #3:
You have arrived at the final accident scene of the day. Two cars of equal mass (2,000 kg each) were involved in a head-on accident at a four-way-stop intersection. Here is what you know:
Car 1 started at rest and coasted toward the intersection from the top of a 50-meter hill.
Car 2 was on a flat stretch of road at the bottom of the hill in front of Car 1.
At the bottom of the hill, before braking, Car 1 was going 30 m/s and Car 2 was going 20 m/s.
From the skid marks on the road you can see that Car 1 applied force on its brakes for 5 seconds, 125 meters before the stop sign where it came to a stop.
There were no skid marks left by Car 2. The collision occurred at the stop sign, where Car 1 had stopped. After the collision, Car 2 came to a stop. Car 1's final velocity is unknown.
1. What was the potential energy of each car at the beginning of the problem? (4 points)

something that i dont know



2. What was the kinetic energy of each car while it was traveling at its maximum speed? (4 points)



i really dont care

3. How much energy did Car 1 "lose" from the top to the bottom of the hill, before it began braking? What happened to this lost energy? (3 points)




blahh
4. How much force did Car 1 apply to the brakes to stop? (3 points)

alot...



5. How much power (in watts) did it take to stop Car 1 by applying force to the brakes? (3 points)

enough



6. What is the momentum of each car right before the accident? (4 points)

the right answer



7. What was Car 1's final speed after the accident? (4 points)

0

[Williams, Sue]

Ashton, I am confused by why you would turn in an assignment like this. Almost everyone had trouble, but asked for help. You have no formulas and no work to show'

0 out of 50 points.

On Tue, Dec 18, 2012 at 10:19 AM, <ashtonly...@gmail.com> wrote:

I. Traffic Accident #1:
It is crash-test-dummy Ed's first day on the job. He (and his 50-kg mass) gets to try out the new 1,200-kg Porsche 911. Lucky Ed! He has to drive it into a brick wall. Unlucky Ed! But it's his job, so he does it.
The Porsche and Ed are moving 30 m/s when they collide with the wall, with an impulse time of 0.5 s.

1. What is the magnitude of their initial momentum? (4 points)

36,000

    0 points

2. What is the magnitude of their final momentum? (3 points)
i dont want to do this

     0 points

3. What is the magnitude of the impulse of the collision? (3 points)

dont even know if ur gonna grade this

     0 points

II. Traffic Accident #2:
You have arrived at the scene of a two-car accident. You know the following pieces of information:
Car 1 and Car 2 have equal masses of 2,000 kg each.
Car 1's initial momentum was 40,000 kg-m/s to the right; Car 2 wasn't moving.
Car 1 collided with Car 2.
Car 1's final velocity is 10 m/s to the right; Car 2's final velocity is unknown.
1. What is each car's initial velocity? (4 points)

56

    0 points

2. What is their total initial momentum? (4 points)

who cares

    0 points

3. After the collision, what is Car 2's final velocity? (4 points)

35

     0 points

4. What is their total final momentum? (3 points)

85

    0  points

III. Traffic Accident #3:
You have arrived at the final accident scene of the day. Two cars of equal mass (2,000 kg each) were involved in a head-on accident at a four-way-stop intersection. Here is what you know:
Car 1 started at rest and coasted toward the intersection from the top of a 50-meter hill.
Car 2 was on a flat stretch of road at the bottom of the hill in front of Car 1.
At the bottom of the hill, before braking, Car 1 was going 30 m/s and Car 2 was going 20 m/s.
From the skid marks on the road you can see that Car 1 applied force on its brakes for 5 seconds, 125 meters before the stop sign where it came to a stop.
There were no skid marks left by Car 2. The collision occurred at the stop sign, where Car 1 had stopped. After the collision, Car 2 came to a stop. Car 1's final velocity is unknown.
1. What was the potential energy of each car at the beginning of the problem? (4 points)

something that i dont know

    0 points

2. What was the kinetic energy of each car while it was traveling at its maximum speed? (4 points)



i really dont care

     0 pointws

3. How much energy did Car 1 "lose" from the top to the bottom of the hill, before it began braking? What happened to this lost energy? (3 points)

     0 points

blahh
4. How much force did Car 1 apply to the brakes to stop? (3 points)

alot...

    0 points

5. How much power (in watts) did it take to stop Car 1 by applying force to the brakes? (3 points)

enough

   0 points

6. What is the momentum of each car right before the accident? (4 points)

the right answer



7. What was Car 1's final speed after the accident? (4 points)

0

   0 points

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