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Ph 201: General Physics I
Chapter 4 Worksheet
1) An 80kg anchor is dropped in the water and plummets to the ocean floor with an observed
acceleration of 3.0 m/s2.
a) Draw a free-body diagram for the anchor.
b) What is the magnitude of the water resistance acting on the anchor?
c) How long does it take the anchor to drop 100m?
2) Draw free body diagrams for the following:
a) a soda can tossed into the air
b) a sea turtle floating in the ocean
c) a possum standing by the side of the road
d) a possum being run over by a car (the moment when the possum is beneath the tire)
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Ph 201: General Physics I
Chapter 4 Worksheet
3) A 50kg box is pulled horizontally along a frictionless floor by a 10N force.
a) Draw a free-body diagram for the box.
b) What is the magnitude and direction of the net force (F) acting on the box?
c) What is the horizontal acceleration of the box?
d) How far does the box travel in 2.5 seconds?
4) A 50 kg box is pulled up a 30o incline along a frictionless floor by a 1000 N force.
a) Draw a free-body diagram for the box.
b) What is the magnitude and direction of the net force (F) acting on the box?
c) What is the magnitude and direction of the acceleration of the box?
e) How long does it take to pull the box 2.0 m up the hill?
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Ph 201: General Physics I
Chapter 4 Worksheet
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5) The motion of a 0.1 kg ball tossed vertically into the air was recorded using a motion detector.
The initial velocity for the ball was 5 m/s (see Graph 1). Analysis of the velocity vs. time graph
yielded the acceleration of the ball during 3 phases of the motion: upward, near the top and
downward (Graph 2). During the upward movement, the average acceleration (aupward) is -12.3
m/s2. Near the top of the trajectory, where air drag was minimal, the average acceleration of
the ball is -10.1 m/s2. During the descent, the average acceleration (adownward) is -7.8 m/s2.
Problems:
a) Observing Graph 1, how does air drag affect shape of the velocity vs. time graph (i.e. the
motion of the ball) compared to no drag?
b) Why is the upward acceleration of the ball greater than at the top or during the descent?
c) Sketch a force vector diagram for each phase of the ball’s motion:
Upward:
At the top:
Downward:
d) Using your force diagrams as reference, apply Newton’s 2nd Law of motion to the ball for
each phase:
Upward:
At the top:
Downward:
e) Determine the average force of air drag on the ball for each phase:
Upward:
At the top:
Downward:
f) For each phase, identify the action-reaction forces that act on the ball:
Upward:
At the top:
Downward:
Ph 201: General Physics I
Chapter 4 Worksheet
Graph 1: Comparison of a tossed ball with (triangles) and w/o (circles) air drag.
Graph 2: Graphical analysis of the phases flight for a vertically tossed ball.
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Ph 201: General Physics I
Chapter 4 Worksheet
6) A 50 kg box is pulled horizontally along a floor against a 30 N frictional force. The observed
net force acting on the box is 100 N.
a) Draw a free-body diagram for the box.
b) What is the magnitude and direction of the net force (F) acting on the box?
c) What is the coefficient of kinetic friction (k)?
c) What is the horizontal acceleration of the box and how far does the box travel in 2.5
seconds?
7) A 50 kg box is pulled up a 30o incline by a 1000 N force. The coefficient of kinetic friction
between the box and the inclined plane is k = 0.25.
a) Draw a free-body diagram for the box.
b) What is the frictional force acting on the box?
c) What is the magnitude and direction of the net force (F) acting on the box?
d) What is the magnitude and direction of the acceleration of the box?
e) How long does it take to pull the box 2.0 m up the plane?
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Ph 201: General Physics I
Chapter 4 Worksheet
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8) A Corvette convertible (mass=1581.8 kg) accelerates in a straight line from 0 to 60 mph with
an elapsed time of 5.5 s on a flat level track. The tires never lose traction with the road surface.
a) Draw a free body diagram for the Corvette during this road test.
b) What is the weight of the Corvette?
c) Apply Newton’s 2nd Law to the Corvette.
d) What is the average net force exerted on the Corvette?
e) What is the minimum coefficient of static friction required to keep the Corvette tires “gripped”
to the track surface?
Ph 201: General Physics I
Chapter 4 Worksheet
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9) A 2 kg block is supported by a flat wooden platform. The platform has an adjustable incline
that can be raised from 0o to 90 o (with respect to the horizontal direction). The coefficient of
static friction between the block and the platform surface is 0.5.
a) As the platform is raised to some angle, , draw the free body diagram for the block as it
sits at rest on the incline.
2 kg

b) Apply Newton’s 2nd Law to the block described in part a.
c) Determine the maximum angle, , that the incline can be raised before the block will begin
to slide.
d) What is the magnitude of the normal force at the angle determined in part c?
e) What is the magnitude of the (maximum) static friction force acting on the block in part c?
Ph 201: General Physics I
Chapter 4 Worksheet
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10. Consider the 2 mass pulley system to the right. Assume the pulley has no mass and there
is no friction between (i) M2 and the surface supporting it and (ii) the pulley itself.
a. Draw free body diagrams for each mass.
M2
b. Apply Newton’s 2nd law to each mass.
M1
c. Determine an equation for the acceleration of the 2 mass system in terms of only the masses
and g.
d. If M1 = 10 kg and M2 = 20 kg, what is the acceleration of the system?
e. Identify as many “Action-Reaction” Force Pairs as you can in this example.
Ph 201: General Physics I
Chapter 4 Worksheet
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11. Consider the same pulley system in Problem 10. In this case, there is friction (static
and/or kinetic) between M2 and the horizontal surface.
a. Draw free body diagrams for each mass.
M2
b. Apply Newton’s 2nd law to each mass.
M1
c. Determine an equation for the acceleration of the 2 mass system in terms of only the masses,
k and g.
d. If M1 = 10 kg and M2= 20 kg, what is the minimum static friction coefficient that will keep the
system from moving?
Ph 201: General Physics I
Chapter 4 Worksheet
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12. How would the pulley system behave if the surface supporting M2 were at an angle (),
pointing upward to the left? Assume there is no friction between M2 and the incline.
a. Draw a diagram of the pulley system described in this problem
b. Draw a free body diagram for each mass.
c. Apply Newton’s 2nd law to each mass.
d. Determine an equation for the acceleration of the 2 mass system in terms of only the masses
and g.
e. If M1 = 10 kg and M2= 20 kg, what is the angle of incline that will keep the system from
moving?