A ball rolls onto the path of your car as you drive down a quiet neighborhood st

Question

A ball rolls onto the path of your car as you drive down a quiet neighborhood street. To avoid hitting the child that runs to retrieve the ball, you apply your brakes for 1.40 s. The car slows down from that 15.0 m/s to 9.00 m/s. The mass of the car is 1140 kg. During the time the brakes were applied, what was the average force exerted on your car? How far did the car move while braking? The weight of an astronaut plus his space suit on the Moon is only 129 N. How much (in N) do they weigh on Earth? (The acceleration due to gravity on the Moon is 1.67 m/s^2 What is the mass (in kg) on the Moon? what is the mass (in kg) on earth?

Explanation / Answer

Acceleration = change in velocity/ time = (15-9)/1.4 = 4.286 m/s2

Force F = 1140(15-9)/1.4= 4885.71 N

Force Direction is opposite to car velocity direction.

b) using v2 - u2 = 2as

2(-4.286) S = -144

S=16.8 m

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