Motion & Newton’s 3rd Law Class Exercises
Physics
1. A 6 kg green bowling ball coasting through deep space at 10 m/s to the right collides with a stationary 4 kg
red bowling ball. The green ball exerts a force of 150 N to the right on the red ball during 0.3 second long
collision. The collision is elastic (they bounce off each other).
(a) Draw a free body diagram for the 4 kg red
(e) Draw a free body diagram for the 6 kg green ball.
bowling ball
(b) What is the net force on the red ball during the
collision?
(f) What is the net force on the green ball during the
collision?
(c) What is the acceleration of the red ball during the
collision?
(g) What is the acceleration of the green ball during
the collision?
(d) What is the velocity of the red ball after the
collision?
(h) What is the velocity of the green ball after the
collision?
2. A 72kg stuntman steps off a rooftop during an action scene and freefalls for 1.3 seconds before landing in
the giant airbag directly below.
(a) Draw the free body diagram for the stuntman as
(e) Draw the free body diagram for the Earth
he freefalls.
(b) What is his acceleration as he falls?
(g) What is the Earth’s acceleration due to the
stuntman (mass of the Earth is 5.974x1024 kg)?
(c) How far does the stuntman freefall?
(h) Assuming the Earth was at rest when the stuntman
jumped, how far did the Earth move?
(d) How fast is he going as he lands?
(i) What is the Earth’s velocity when the stuntman
lands?
3. 67 kg Shannon is standing on the floor of her studio and firing 10 g paintballs at a canvas hanging on wall
for an art project. Each paintball is fired from rest, accelerates down the 40 cm long barrel for 0.2 s and comes
out going 40 m/s. The coefficient of friction between Shannon’s feet and the ground is 0.5.
(a) Draw a free body diagram of the paintball as it is
(c) Draw a free body diagram of Shannon as she fires
being fired.
the paintball
(b) What is the paintball’s acceleration while in the
barrel?
(d) What is Shannon’s acceleration as the gun fires?
(c) How much force does the gun (and Shannon)
exert on the paintball?
(e) What is Shannon’s velocity after firing the$
paintball?
4. Bryce is playing catcher in a game of softball. The pitcher throws a ball at 25 m/s, which whizzes past the
batter and into Bryce’s mitt. During the catch, the ball comes to rest in 0.2 seconds. The coefficient of friction
between Bryce and the ground is 0.8
(a) Draw the free body diagram for the ball as Bryce
(d) Draw the free body diagram for Bryce during the
is catching it.
catch.
(b) What is the acceleration of the ball as it is being
caught?
(e) Calculate the acceleration of the goalie.
(c) What force does Bryce exert on the ball?
(f) What is the goalie’s velocity after the half second
push?
5. Karen, with a mass of 58 kg, is sledding down a hill. When she reaches the end of the hill, she continues
coasting along the flat ground, heading straight for a 140 kg outhouse! Karen hits the outhouse going 12 m/s and
comes out of the 0.5 s long impact going 2 m/s The coefficient of friction between the outhouse and the snow is
0.3. The coefficient of friction between Karen’s sled and the snow is 0.25.
(a) Draw a free body diagram for Karen
(e) Draw a free body diagram for the outhouse.
(b) What is Karen’s acceleration during impact?
(f) What is the net force acting on the outhouse
during the collision?
(c) What is the net force on Karen?
(g)What acceleration does the outhouse experience?
(d) How much force does the outhouse exert on
Karen?
(h) How fast is the outhouse going after impact?
6. In order to jumpstart his stalled 500 kg car, 63kg Marcus pushes it along the flat ground. He pushes it for a
distance of 10 meters and gets it going 8 m/s. The coefficient of friction between the car and the ground is 0.13.
(a) Draw the free body diagram of the car.
(e) Draw a free body diagram for Marcus.
(b) What is the car’s acceleration?
(e) How quickly is Marcus accelerating? [Hint:
what is he pushing?]
(c) What is the net force on the car?
(f) What force keeps Marcus from getting pushed
backwards?
(d) What force does Marcus apply to the car?
(g) How strong is that force?