An automobile has a mass of 900 kg (about a ton). It travels east at 25 m/s (jus

Question

An automobile has a mass of 900 kg (about a ton). It travels east at 25 m/s (just about 56 mph which is speeding, almost) when it hits a slippery stretch of highway. The driver loses control of the car, hits a rigidly fixed guard rail, and rebounds at 20 m/s moving at an angle of 36.6 degrees N of E after the collision.

a. Calculate the initial momentum of the car.

b. Calculate the final momentum of the car.

c. Find the magnitude and direction of the change in momentum of the car.

d. If the contact with the guard rail lasted 0.6 seconds, what was the average force acting on the car?

Explanation / Answer

initial momentum = 900* 25 = 22500kg-m-s

final mometum = 900* 20= 1800 kg-m-s

c) change of momentum in east direction = 22500- 1800 *sin(36.6) = 21426.79 kg-m-s

change in momentum in north direction= 1800 cos( 36.6) = 1445.07 kg-m-s

do net change= sqrt(( 21426.79 )2+( 1445.07 )2) =21474.34 kgm/s

direction = arc tan( 1445.07/21426.79) = 3.85 degrees

d) avg force = change in momentum / del T= 21474.34 kgm/s/0.6= 34790.56 N

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