A friend asked for help with a problem, and I tried to go about it as logically as possible. His class is different, so I wasn’t really sure how far into it they were and what equations to use. Anyway, I wanted to make sure we didn’t get it wrong. Could someone check it, please? I’m especially concerned that we never took direction into account, and that we weren’t sure how to take the law of conservation of momentum into account.

1. The problem statement, all variables and given/known data

A 1,988 kg car is moving at 43 m/s east. Suddenly, the driver slams on the brakes for 1.8 seconds, exerting a force of 6,000 N to the car.

A. What is the initial momentum of the car?

B. What is the change in momentum?

C. What is the final momentum of the car?

D. What is the final velocity of the car?

2. Relevant equations
a=f/m
v=v0+at
p=mv

3. The attempt at a solution

A. What is the initial momentum of the car?
p=mv
p=1988*43
p=85484 kg m/s

B. What is the change in momentum?
85484 kg m/s-74669 kg m/s=10815 kg m/s
C. What is the final momentum of the car?
p=1988*37.56 m/s
p=74669 kg m/s

D. What is the final velocity of the car?
a=f/m
a=6000/1988
a=-3.02 m/s^2
v=43+-3.02*1.8
v=37.56 m/s^2

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