# Homework Help: Impulse for a car when it drives in a circle

1. Feb 22, 2012

### iamhe

1. The problem statement, all variables and given/known data
A 1400kg car is driving at a constant velocity, 5.3 m/s. It turns 90 degrees in 4.6 seconds. And then it slams into a tree and it takes 350 ms to stop the car.
What is the impulse on the car (a) due to the turn? (b)Due to the collision with the tree?
What is the magnitude of the average force that acts on the car (c)during the turn? (d)During the collision with the tree?
What is the angle between the average force in (c) and the positive x direction?

2. Relevant equations
Impulse = j = p2-p1 = mv2-mv1
F = ma

3. The attempt at a solution
a) 0. Since the velocity does not change, and the mass is constant, there is no change between p1 and p2.
b) j = (1400)(5.3) - (1400)(0) = 7420
c) F = 0/(4.6) = 0
d) F = (7420)/(0.350) = 21200
e) I have absolutely no clue on how to even start this one.

Thanks in advance for any help!

2. Feb 22, 2012

### SHISHKABOB

Well for the parts where the car is making the turn, there's a force that you might be forgetting about. Basically, during the turn, the car is in Uniform Circular Motion for a quarter of a circle.

3. Feb 22, 2012

### iamhe

If I am not given the radius of the turn, how can I still use the uniform circular motion formula?

4. Feb 23, 2012

### SHISHKABOB

You're given the time it took to make a quarter of a circle and you're given the tangential speed during the turn. There's a relationship between those that will give you the radius.