A car is heading 43 m/s east. Find momentum, velocity

In summary, the conversation involved a request for help with a physics problem and the use of different equations to solve it. The final solution was obtained using the impulse-momentum theorem. The individual is seeking confirmation of their answer from someone else since their teacher did not provide a solution.
  • #1
Medgirl314
561
2
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.

Thanks in advance!

Homework Statement



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?

Homework Equations


a=f/m
v=v0+at
p=mv


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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  • #2
Medgirl314 said:
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.

Thanks in advance!

Homework Statement



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?

Homework Equations


a=f/m
v=v0+at
p=mv


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
My guess is that it's intended for this question to be answered using impulse.

Apply the Impulse - Momentum Theorem.

The solution is fairly simple to obtain that way.
 
  • #3
Wow, I can't believe how much I over-complicated that one. Oops. He said he re-worked it with the theorem and got the same answer.Thank you!
 
  • #4
Could someone please confirm if this is the right answer? His physics teacher didn't provide a solution.
 
  • #5
Medgirl314 said:
Could someone please confirm if this is the right answer? His physics teacher didn't provide a solution.

What do you get using Impulse & Momentum ?
 

FAQ: A car is heading 43 m/s east. Find momentum, velocity

1. What is momentum and how is it calculated?

Momentum is a measure of an object's motion and is calculated by multiplying its mass by its velocity. In this case, the momentum of the car can be calculated by multiplying its mass in kilograms by its velocity in meters per second.

2. How is velocity defined and why is it important?

Velocity is a measure of an object's speed and direction of motion. It is important because it helps us understand how an object is moving and how it will continue to move in the future.

3. How is the direction of an object's velocity represented?

The direction of an object's velocity is represented by a vector. In this case, the car's velocity of 43 m/s east means that it is moving eastward at a speed of 43 m/s.

4. Can momentum be negative?

Yes, momentum can be negative if the object is moving in the opposite direction of the chosen positive direction. In this case, if east is chosen as the positive direction, the car's momentum would be -43 kg*m/s.

5. How does the momentum of an object affect its motion?

The momentum of an object is directly proportional to its mass and velocity, meaning that the greater the momentum, the harder it is to change the object's motion. This is known as the law of conservation of momentum, which states that the total momentum of a system remains constant unless acted upon by an external force.

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