Name _______________________
Forces and Motion Worksheet
SHOW YOUR WORK!
The direction of gravitational acceleration, g, is ALWAYS downward. Gravity always pull objects
downward at g = 9.8 m/sec^2 but we tend to use g = 10 m/sec^2 in worksheet problems. We
will usually assume free fall conditions, which means only gravity is involved. When something
is “dropped” it always means it has an initial speed of 0 m/sec (from rest). Otherwise the object
will start at a non-zero speed (thrown, tossed).
Speed describes how fast an object is traveling (m/sec, miles/hr, km/sec, etc). Acceleration is
how fast its speed is changing (m/sec/sec, m/sec2).
speedfinal = speedinitial + (grav accel) x time
sf = si + gt
1. A penny is dropped from the top of a building. What is its speed after 2 sec? After 5 sec?
2. Suppose a free-fall ride at an amusement park starts at rest and is in free fall. What is the
speed of the ride after 3.7 s?
3. A penny is thrown from the top of a tall building with an initial speed of 5 m/sec. How fast is
it moving after 2 sec? After 5 sec?
1.) A net force of 7.5 kN, west acts on a 1208 kg race car.
At what rate will the car accelerate? (a = 6.2 m/s2, west) Solution
2.) A car, mass 1485 kg, travelling south at 116 km/h, slows to a stop in 10.25 seconds.
What is the magnitude and direction of the net force that acted on the truck?
(F = 4.67 kN, north) Solution
Name _______________________
3.) Find the net force acting on a fridge if the applied forces are 378.4 N, west
and 401.3 N, west while the force of friction is 67 N. (FNet = 713 N, west) Solution
4.) A large box moving across a floor at constant speed has two people moving it.
One is pushing 236.1 N from behind while the other is pulling 89.3 N from the front.
What is the force of friction? (Ff = 325.4 N, opposite to the direction of motion) Solution
5.) Find the acceleration of a 20.0 kg curling stone if the applied force is 88.7 N, west
and the force of friction is 29.73 N. (a = 2.95 m/s2, west) Solution
Name _______________________
6.) A broken down car, mass 1418 kg, is accelerated at 1.65 m/s2, south when pulled by a tow
truck.
What is the force of friction if the tow truck exerts 2.63 kN, south on the car?
(Ff = 0.29 kN, north) Solution
7.) Find the weight (force of gravity) of an exactly thirty kilogram mass. (Fg = 294 N, down) Sol
8.) A five kilogram mass lays on a floor. What force does the floor exert on the object?
(FA = 49 N, upward)
Solution
9.) A person of mass 81 kg throws a 2.15 kg ball with a force of 20.8 N, west.
Find the acceleration of both ball and person ignoring friction.
( aball = 9.67 m/s2, west ;
aman = 0.26 m/s2, east )
Solution
Name _______________________
10.) A 55.0 kg woman climbs at a constant velocity up a rope.
a) What force does the rope exert on the woman? ( FA = 539 N, upward )
b) What force does the woman exert on the rope? ( FA = 539 N, downward )
c) How would the answers to a) and b) change if she was descending? Solution
11.) A 4850 kg helicopter accelerates downward at 1.58 m/s2.
Solution
What force is exerted by the air on the propellers? ( FA = 39.9 kN, upward )
12.) A horizontal force of 26.3 N is necessary to push a 99 N wooden box across a tile floor
at constant velocity. Find the coefficient of sliding friction between the two surfaces.
( μ = 0.27 )
Solution
Name _______________________
13.) The coefficient of sliding friction between rubber tires and wet pavement is 0.65.
The brakes are applied to a 1000 kg car traveling west and it skids to a stop.
Find the force of friction the road exerts on the car. ( Ff = 6.3 kN, east ) Solution