Dynamics Review Problems
1.) Which one of Newton’s Laws explain why when an astronaut, who is in space, will
move backwards if they are holding an aerosol can and spray some of the contents
out? [Newton’s 3rd Law]
2.) Which one of Newton’s Laws explain why a heavier car will accelerate slower than a
lighter car? [Newton’s 2nd Law]
3.) Which one of Newton’s Laws explain why it is harder to get a stationary object
moving that it is to keep a moving object in motion? [Newton’s 1st Law]
4.) What is another name for Newton’s 1st Law of motion? [Inertia]
5.) A car with a mass of 1225 kg, travelling at 105 km/h east, slows to a stop in 53m.
What is the net force acting on the car? [9.8x103 N, west]
6.) An 1125kg pickup truck is traveling north along a level road at 15.0 m/s. The truck
applies the brakes and comes to a stop. If the force of friction acting on the truck is
4.41x103N, what is the distance it takes the truck to skid to a stop? [28.7 m]
7.) Two people are pushing a stalled 2000kg truck along a level road. One person
exerts a force of 300N, east and the second person exerts a force of 350N, east.
The magnitude of the force of friction on the truck is 550N. Calculate the acceleration
of the truck. [0.0500m/s2, east]
8.) A car if moving along a horizontal road at a constant velocity of 12.0m/s, west. If the
force of friction acting in the car is 163N, what is the force applied acting on the car?
[ 163N, west]
9.) What is the weight of a 108 kg football player? [1.06x103N]
10.) A 52N sled is pulled across a cement sidewalk at constant speed. A horizontal
force of 36N is exerted to move the sled. What is the coefficient of friction between
the sidewalk and the sled? [0.69]
11.) A force of 31N is needed to start an 8.0kg steel slider moving along a horizontal
steel rail. What is the coefficient of static friction? [0.40]
12.) A puppy is pushing his 4.35kg toy along the carpet. The puppy exerts a force of
14.5N on the toy to move it along the carpet. If the coefficient between the toy and
the carpet is 0.116, what is the magnitude of acceleration of the toy? [2.20 m/s2]
13.) Two masses are connected by a light rope over a light, frictionless
pulley as shown in the diagram. The masses of each block are 25 kg
and 35 kg.
a. Calculate the acceleration of the 35kg mass. [1.6 m/s2, down]
b. Calculate the magnitude of tension in the string. [2.9x102 N]
14.) A 400g mass is overhanging off the edge of a
table and is connected to a 600g mass that is
sliding along a horizontal surface, as shown in the
diagram. The coefficient of friction between the
600g mass and the surface is 0.0560.
a. Calculate the magnitude of acceleration of
the 600g mass. [3.59 m/s2]
b. Calculate the magnitude of tension in the
string. [2.49 N]
15.) What is the magnitude of tension in the cable of a 1.20x103kg elevator that is
accelerating downward at a rate of 1.05m/s2? [1.05x104 N]
16.) A person riding in an elevator has an apparent weight of 120N. If the person has a
true weight of 108N, what is the acceleration of the elevator? [1.09m/s2, up]
17.) The maximum force a grocery bag can withstand and not rip is 250 N. If 20.0kg of
groceries are lifted from the floor to the table with an acceleration of 5.00m/s 2, will the
bag hold? [ T=296.2N, therefore the bag will not hold]
18.) If one person is pulling on an object with 37.1 N to the west and another person is
pushing the same object with 49.5 N to the north, what is the net force on the object?
[61.9N, 36.9o W of N]
19.) Two teenagers push on a heavy crate. Dion pushes with a force of 185 N, east and
Joan (who is confused with the direction at which he should be pushing) is pushing
with a force of 195 N, 60.0o W of N. What is the resultant/net force on the crate?
[98.8 N, 9.39o E of N]
20.) An object that has a mass of 45.0 kg is pulled along a horizontal surface by a rope
that makes an angle of 32.0o with the horizontal. If the force of friction is 50.0 N and
the tension in the rope is 95.0 N, what is the magnitude of acceleration of the object?
[0.679 m/s2]
21.) Find the magnitude of tension in each rope
that is used to hang the sign, as indicated in
the diagram. [T1 = 33.6N & T2 = 92.2N]
22.) A 325 N box is sliding down a frictionless inclined plane. If the incline makes an
angle of 30.0o with the horizontal, what is the acceleration along the incline?
[4.91 m/s2, down incline]
23.) A 7.6 kg object is sliding down an incline at a constant velocity. If the incline makes
an angle with the horizontal of 33o, and what is the coefficient of friction? [0.65]
24.) You slide a 33.1kg crate up a 20.0o inclined plane with an acceleration of 0.85m/s2
by exerting a force of 489 N parallel to the inclined plane.
a. What is the force of friction? [3.5x102 N, down incline]
b. What is the coefficient of friction? [1.1]