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Problems Chapter 6
Forces and Equilibrium
1. Rodney’s pickup truck breaks down and he must push the truck to a nearby station. He applies a force of
550 newtons to the truck to overcome a frictional force of 125 newtons.
a. Calculate the mass of the truck if Rodney’s pushing causes the truck to accelerate at a rate of
0.200 m/s2.
b. Calculate the weight of Rodney’s pickup truck in newtons.
c. Use the diagram of the truck to create a free-body diagram of the forces applied to the truck.
2. Fletcher is standing in a super-fast elevator that accelerates upward at a rate of 14.7 m/s2. Fletcher’s
mass is 110 kilograms.
a. Calculate Fletcher’s weight while he stands stationary on Earth’s surface.
b. What would be the reading on a bathroom scale (in newtons) if Fletcher were standing on the scale
in the elevator when it accelerates upward?
3. An amusement park ride accelerates Brandy straight down at a rate of 4.90 m/s2. If Brandy’s mass is
60.0 kilograms, what is her apparent weight on the amusement park ride?
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Skill Sheet
Forces and Equilibrium
4. A copper plate weighing 120 newtons is resting on a steel floor. Just as Aurellia tries to pull the plate
across the steel floor, her baby brother, Arturo, crawls onto the plate. In order to just start the plate
moving, Aurellia must apply a force of 106 newtons.
a. What is the normal force applied by the floor on the plate supporting Arturo?
b. How much does Arturo weigh? (static for copper on steel is 0.53)
c. What is Arturo’s mass?
5. A 25.0-kilogram space probe fell freely with an acceleration of 2.00 m/s2 just before striking a distant
planet. What would be the weight of the space probe on the distant planet?
6.
The diagram below pictures a 0.5-newton metal disk resting on an index card balanced on top of a glass
container.
a. What is the net force acting on the metal disk?
b. Use the diagram to make a free-body diagram of the forces acting on the metal disk.
7. Ashanti walks into school on a rainy day. As Ashanti, who weighs 580 newtons, steps on the floor, the
water on his shoes suddenly reduces the coefficient of friction on the tile floor to 0.050. What is the
sliding frictional force between Ashanti and the tile floor?
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Skill Sheet
Forces and Equilibrium
8. Meg brings Buddy, her 60.0-kilogram dog, to the veterinarian. Buddy does not like to visit the vet’s
office and so stops at the door. To get the dog to the receptionist’s desk, Meg has to push Buddy across
the floor with a force of 225 newtons. What is the coefficient of sliding friction between the floor and
Buddy?
9. Horizontal forces are applied to a 20.0-newton wooden block as shown in the drawing below. The net
force causes the wooden block to move across a wooden floor.
a. Calculate the net force acting on the wooden block.
b. Calculate the magnitude of the frictional force acting on the box.
(sliding for wood on wood = 0.20)
c. Calculate the mass of the wooden block.
d. Calculate the acceleration of the wooden box.
10. When 75.0 newtons are hung from a vertically suspended spring, the spring stretches 0.25 meters.
a. Calculate the spring constant for this spring.
b. If a second spring has a spring constant of 100 N/m, would the spring be more rigid or more loose
than the spring above?
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Skill Sheet
Forces and Equilibrium
11. A student performed an experiment in which a weight was attached to a spring and the total length of the
spring measured. A second weight was added and data recorded. The data from the exercise are in the
table below. Calculate the spring constant for the spring used in the experiment.
Attached Weight (N)
0.98
1.96
Total Spring Length (m)
0.37
0.42
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