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Forces Problem Set
**********Be sure to draw a proper Free Body Diagram for EVERY question!*************
You may also wish to summarize your notes on forces and friction briefly before you begin.
1) An astronaut finds that the force of gravity on her is 1.83  103 N on a certain planet and 6.86 
102 N on earth. What is the acceleration due to gravity on the other planet? [26.1 m/s 2]
2) A 12.0 kg object is pushed with a horizontal force of 6.0 N across a horizontal table. If the force
of friction between the two surfaces is 2.0 N, what is the acceleration of the object? [0.33 m/s 2]
3) A 20.0 kg object is pulled horizontally along a level floor with an applied force of 27.0 N. If this
object is accelerating at a rate of 0.80 m/s2, what is the magnitude of the force of friction? [11N]
4) An object that has a mass of 36.0 kg is pushed along a horizontal surface with a force of 85.0
N. If the force of friction is 72.0 N, what is the acceleration of the object? [0.361 m/s 2]
5) A horizontal force of 90.0 N is required to push a 75.0 kg object along a horizontal surface at a
constant speed. How large is the force of friction? [90.0 N]
6) While standing on a horizontal frictionless surface, a 50.0 kg student pushes against a wall with
an average force of 125 N for 0.110 s.
a) Calculate the velocity of the student after this 0.110 s. [0.275 m/s]
b) Calculate the velocity of the wall after the 0.110 s, if it is attached to the Earth, and the
Earth’s mass is 5.98  1024 kg. [2.3  10-24 m/s or really really REALLY slow]
7) The front end of a 1000 kg car travelling at 100 km/h buckles inward by 0.800 m when it
collides with a brick wall and comes to rest. What force is exerted by the car on the wall? [4.8 
105 N]
8) A man stands on a bathroom scale in an elevator. The scale reads 1500 N when the elevator
accelerates upward at 5.50 m/s2.
a) What is the woman’s mass? [98 kg]
b) What is the acceleration of the elevator when the scale reads 1000 N? [0.20 m/s 2 up]
9) **Two carts on a frictionless surface, each with mass 10.0 kg, are connected by a heavy rope of
mass 2.00 kg. If one cart is pulled horizontally by a force of 66.0 N,
a) What is the acceleration of the carts and the rope? [3.0 m/s2]
b) How hard does the rope pull on the rear cart? [30 N]
c) How hard does the rope pull on the front cart? [-36 N]
Forces Problem Set
**********Be sure to draw a proper Free Body Diagram for EVERY question!*************
You may also wish to summarize your notes on forces and friction briefly before you begin.
1) An astronaut finds that the force of gravity on her is 1.83  103 N on a certain planet and 6.86 
102 N on earth. What is the acceleration due to gravity on the other planet? [26.1 m/s 2]
2) A 12.0 kg object is pushed with a horizontal force of 6.0 N across a horizontal table. If the force
of friction between the two surfaces is 2.0 N, what is the acceleration of the object? [0.33 m/s 2]
3) A 20.0 kg object is pulled horizontally along a level floor with an applied force of 27.0 N. If this
object is accelerating at a rate of 0.80 m/s2, what is the magnitude of the force of friction? [11N]
4) An object that has a mass of 36.0 kg is pushed along a horizontal surface with a force of 85.0
N. If the force of friction is 72.0 N, what is the acceleration of the object? [0.361 m/s 2]
5) A horizontal force of 90.0 N is required to push a 75.0 kg object along a horizontal surface at a
constant speed. How large is the force of friction? [90.0 N]
6) While standing on a horizontal frictionless surface, a 50.0 kg student pushes against a wall with
an average force of 125 N for 0.110 s.
a) Calculate the velocity of the student after this 0.110 s. [0.275 m/s]
b) Calculate the velocity of the wall after the 0.110 s, if it is attached to the Earth, and the
Earth’s mass is 5.98  1024 kg. [2.3  10-24 m/s or really really REALLY slow]
7) The front end of a 1000 kg car travelling at 100 km/h buckles inward by 0.800 m when it
collides with a brick wall and comes to rest. What force is exerted by the car on the wall? [4.8 
105 N]
8) A man stands on a bathroom scale in an elevator. The scale reads 1500 N when the elevator
accelerates upward at 5.50 m/s2.
a) What is the woman’s mass? [98 kg]
b) What is the acceleration of the elevator when the scale reads 1000 N? [0.20 m/s 2 up]
9) **Two carts on a frictionless surface, each with mass 10.0 kg, are connected by a heavy rope of
mass 2.00 kg. If one cart is pulled horizontally by a force of 66.0 N,
a) What is the acceleration of the carts and the rope? [3.0 m/s2]
b) How hard does the rope pull on the rear cart? [30 N]
c) How hard does the rope pull on the front cart? [-36 N]