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# Car acceleration and net force

1. Suppose a man pushes a small car on level ground. He pushes with a force of 400 N, and the 800kg car accelerates at a rate of 0.30 m/s2.

(a) What is the net force on the car?
(b) Draw a force diagram for the car, showing the force of pushing, the force of friction, and weight, and the upward (normal) force of the ground.
(c) Determine the force of friction.
(d) Suppose the man stops pushing. What then would be the acceleration of the car (magnitude and direction)?

2. Suppose a bowling ball weighs 12 pounds on the surface of the Earth. Now suppose we take the ball to a distance D from the center of the Earth, where D is 60 times the Earth's radius. What is the force of Earth's gravity on the bowling ball in this case? If you dropped the bowling ball from that height, what would be its acceleration, at first? (You don't need to know the constant G or the mass or radius of the Earth.)

#### Solution Preview

1. (a) The acceleration of the car would be equal to the net force along the direction of movement divided by the total mass.

Fnet = net force
m = total mass
a = Fnet / m
0.3 = Fnet / 800
Fnet = 240 N

(b) See file attached

(c) The force he applies: Fapp=400N Frictional force: Ffrict total mass: m = 800 kg acceleration: a= 0.3 m/s2

The net force on the car would be the sum of applied force and ...

#### Solution Summary

Calculating the net force and acceleration of a car and a bowling ball.

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