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Review Problems for Unit 3
For each problem draw a force diagram that would be accepted on the AP exam, show all work, and write out
the sum of force/equation that is needed.
1. A 1240 kg wrecking ball is pulled up and over by a wire. (a) What is the tension in the wire and (b) how
hard is the wall pushing on the ball?
10q
2. A 9.34 kg object slides down the hill. (a) What is the normal force on the object? (b) What is the frictional
force on the object if it moves at a constant velocity? (c) If the surface has a coefficient of friction equal to
0.3, what is the new frictional force and what is the acceleration of the object?
27q
Unit 3: Newton’s Laws of Motion
Page 1 of 4
3.
(a) What is the normal force and (b) what is the force of friction for the situation below if the box isn’t
moving? (c) What would be the coefficient of friction is the box accelerates at 3 m/s2 to the right?
F = 10 N
42q
m =25kg
4. A mass of 15 kg hangs as shown below with 3 strings attached. The tension is string 1 is 283 N, find the
tension is the other two strings.
String 2
41o
String 1
String 3 – being
pulled down
5. A 50 kg ball rests motionless on the incline because of the tension in the rope. Assuming there is no
friction, (a) what is the tension in the rope and (b) the normal force acting on box?
String
19o
Unit 3: Newton’s Laws of Motion
Page 2 of 4
6. A 5.0-kilogram monkey hangs initially at rest from two
vines, A and B, as shown above. Each of the vines has
length 10 meters and negligible mass. Determine the
tension in vine B while the monkey is at rest.
7. A 10-kilogram block rests initially on
a table as shown in cases I and II above.
The coefficient of sliding friction
between the block and the table is 0.2.
The block is connected to a cord of
negligible mass, which hangs over a
massless frictionless pulley. In case I a
force of 50 N is applied to the cord.
In case II an object of mass 5 kilograms is hung on the bottom of the cord. (a) Calculate the acceleration of the
10-kilogram block in case I. (b) Calculate the acceleration of the 10-kilogram block in case II.
Unit 3: Newton’s Laws of Motion
Page 3 of 4
8. A 55 kg women is in an elevation at rest. (a) What is the normal force acting on the women if the elevator
starts to accelerate down at 4 m/s2? (b) What is the normal force acting on the women when the elevator starts
to slow down at 2 m/s2?
9. A rotten pumpkin that has a mass of 9 kg is dropped and is moving at a speed of 17 m/s right before it hits
the ground. (a) What is the acceleration of the pumpkin during impact if it stops in 0.22 s? (b) What force does
the ground exert on the pumpkin during impact with the ground? (c) What force does the pumpkin apply to the
ground during impact?
Unit 3: Newton’s Laws of Motion
Page 4 of 4