A 500 kg car is moving at 40 m/s. What is the impulse needed to stop this car?

Question

I found the momentum (20,000 ns)

 

the other things the question asks is:

if this car takes 15 sec to stop, what is the average braking force?

what is the time rate of change in momentum?

Answer 1

Deceleration of the car = 40/15 = 8/3 m/s²

The braking force F = ma = 500*8/3 = 4,000/3 N = 1,333 N

Impulse = F*(change of time) = 4,000/3 * 15 = 20,000 kg-m/s

(Note by conservation of momentum, the momentum before the impact = 500*40 = 20,000)

Rate of change in momentum = net force applied to the object = 1,333 N = 1,333 kg-m/s/s