Question

Suppose a child drives a bumper car head on into the side rail, which exerts a force of 3400 N on the car for 0.400 s. (Assume the initial velocity is in the positive direction.)
(a)What impulse (in kg · m/s) is imparted by this force? (Indicate the direction with the sign of your answer.)
(b)Find the final velocity (in m/s) of the bumper car if its initial velocity was 3.30 m/s and the car plus driver have a mass of 200 kg. You may neglect friction between the car and floor. (Indicate the direction with the sign of your answer.)
Q2: Compare the kinetic energy of a 22,000 kg truck moving at 120 km/h with that of an 82.0 kg astronaut in orbit moving at 28,000 km/h.

Answer 1

Answer a) impulse is 1360 kg.m/s

Explanation: impulse is impact force times the time of impact

I = 3400 * 0.4 = 1360kg.m/s

Answer b) final velocity is 10.1m/s

Explanation: impulse is the change of momentum

I = m(v-u)

V and u are final and initial velocities respectively.

1360 = 200 (v - 3.3)

1360 = 200v - 660

V = (1360+660)÷200

V = 10.1m/s

Q2 answer is: astronaut has KE approximately 208 times that of the truck

Explanation :

KE = 0.5mv^2

For truck

KE = 11000 * 33.3^2 = 12197790J

For astronaut

KE = 42 * 7777.7^2 = 2540689926J

Comparing

2540689926/12197790 = 208.2

NB: speed has been converted to m/s by multiplying with 0.28 I.e 1000/3600