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SPH 4U
Dynamics & Statics Review
1.
The FBD of a wagon being pulled along a horizontal surface is best represented by
2.
The free-body diagram of a block being pushed up a rough ramp is best represented by
3.
An object sits at rest on a ramp. Which of the following free-body diagrams best represents the forces
acting on the object?
4.
An
a)
b)
c)
5.
An object is pushed horizontally at a constant velocity. What can correctly be said about the forces acting
on the object?
a) The force(s) acting forward is/are greater than the force(s) acting backward.
b) The sum of all forces has a value directed forward.
c) The sum of all forces is zero.
d) The forces acting on the object can be said to be “unbalanced.”
e) Newton’s second law best summarizes the effect of the forces acting on the object.
6.
An elevator accelerates downward. What is the relationship between the gravitational force
object has two forces acting on it: 8.4 N [S] & 7.5 N [E]. The magnitude of the net force is
1.3  102 N
d) 4.0 N
16 N
e) 0.9 N
11 N
the elevator and the tension
in the cable that supports the elevator?
a)
d)
b)
e)
c)
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acting on
7.
A force of 12 N acting in a direction [30ºE of S] is equivalent to which of the following pairs of forces
acting simultaneously?
a) 24 N [S], 14 N [E]
d) 6 N [S], 10 N [E]
b) 14 N [S], 24 N [E]
e) 10 N [S], 6 N [E]
c) 12 N [S], 12 N [E]
8.
A 24-kg traffic light is suspended from the midpoint of a cable suspended between two poles. The angle
between the cable and the pole is 80 at both poles. The net force acting on the traffic light has a value of
a) zero
d) 2.4  102 N
b) 47 N
e) 4.6  102 N
c) 82 N
9.
Two masses, A and B, hang on opposite ends of a rope suspended over a pulley. The mass of A is greater
than the mass of B. If
represents the force of tension exerted by the rope on mass A and
represents the force of tension exerted by the rope on mass B, then which of the following statements
concerning the forces of tension is true?
a)
d)
b)
e)
c)
10. Two masses hang on opposite ends of a rope suspended over a pulley. The pulley is restrained from rotating
and the two forces:
(the force of tension exerted by the rope on mass A) and
(the force of
tension exerted by the rope on mass B) are found to be equal in magnitude. If the pulley becomes free to
rotate and the system begins moving, the relationship between those forces becomes
a)
d)
b)
e)
c)
11. A 1.5-kg cart is pulled with a force of 7.3 N at an angle of 40 above the horizontal. If a kinetic friction
force of 3.2 N acts against the motion, the cart’s acceleration along the horizontal surface will be
a) 5.0 m/s2
d) 1.6 m/s2
2
b) 2.7 m/s
e) 1.0 m/s2
2
c) 2.4 m/s
12. An object sits at rest on a ramp. As the angle of inclination of the ramp increases, the object begins to
slide. Which of the following explanations best accounts for the object’s movement?
a) The coefficient of static friction has decreased sufficiently.
b) The force of gravity acting on the object has increased sufficiently.
c) The component of gravity along the ramp has increased sufficiently.
d) The friction has decreased sufficiently while the normal force has remained unchanged.
e) The normal force has increased sufficiently.
13. The acceleration of an object sliding along a frictionless ramp that is inclined at an angle  is
a) g cos
d) g
b) g sin
e) zero
c) g tan
14. A 2.0-kg object is pulled horizontally by a force of 6.3 N along the floor where the coefficient of kinetic
friction is 0.24. What is the object’s acceleration?
a) 5.5 m/s2
d) 1.6 m/s2
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b)
c)
2.0 m/s2
2.0 m/s2
e)
0.80 m/s2
15. A 1.4-kg object is pulled horizontally along the floor against 3.2 N of kinetic friction. If the object
accelerates at 5.8 m/s2, what is the value of the applied force?
a) 26 N
d) 6.4 N
b) 11 N
e) 4.9 N
c) 10 N
16. For the system at right, block A on the inclined plane has a
mass m, and g is the gravitational acceleration. The magnitude
of the component of the force of a gravity parallel to the plane
is
a)
FN cosθ
c)
FN sinθ
b)
mg cosθ
d)
mg tan θ
A
B
θ
e)
mg sinθ
17. The total force, applied at an angle θ, needed to drag a box at constant speed across a horizontal surface
with coefficient of kinetic friction μk is
a)
mg  k mg cos 
b)
mg  k mg sin 
d)
k mg
cos   k sin 
e)
None of the above
c)
mg
cos   k sin 
18. A 3.0 kg object is released on a frictionless plane inclined at 60˚to the horizontal. The unbalanced force
acting on the object is in N
a)
0
b)
10
c)
15
d)
30
e)
25
19. According to Newton's second law, the acceleration of an object is directly proportional to the net force
applied to it. A student applies a constant force F to a wooden block which is free to slide on a table, and
measures the resulting acceleration a. He then applies twice the force and finds that the acceleration has
tripled. Which one of the following statements is the correct conclusion to draw from this result?
a)
Newton's second law is not valid under these conditions.
b)
There is a frictional force of 21 F on the block.
c)
There is a frictional force of
d)
There is a frictional force of
e)
There is a frictional force of
1
4
2
3
1
3
F on the block.
F on the block.
F on the block.
20. A heavy weight is supported by two cables that exert tensions of magnitude T1 and T2.
Which statement is correct?
a)
T1 = T2
b)
T1y = T2y
c)
T1 > T2
d)
T1 < T2
e)
We need the mass of the box to determine the correct answer.
21. For an object sliding on a ramp, what is the most appropriate way of resolving the forces? Why is this
method superior to others?
22. A spider builds its web in a window frame that is lying on the ground. It is supported by four main strands.
Calculate the force of tension in strand 4 assuming the web is stable. The tensions in the other three
strands are as follows:
strand 1:
21 mN [20°E of N]
strand 2:
16 mN [60°E of S]
strand 3:
18 mN [40°W of S]
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23. A force of 3.5 N [60°E of N] and a force of 2.8 N [40°W of S] act on the same object. Find the net force
acting on the object using (a) a trigonometric method and (b) a component method.
24. A pulley device is used to hurl projectiles from a ramp (μk = 0.26) as
illustrated in the diagram. The 5.0-kg mass is accelerated from rest
at the bottom of the 4.0 m long ramp by a falling 20.0-kg mass
suspended over a frictionless pulley. Just as the 5.0-kg mass
reaches the top of the ramp, it detaches from the rope (neglect the
mass of the rope) and becomes projected from the ramp.
a)
b)
c)
d)
Determine the acceleration of the 5.0-kg mass along the ramp.
(Provide free-body diagrams for both masses.)
Determine the tension in the rope during the acceleration of the 5.0-kg mass along the ramp.
Determine the speed of projection of the 5.0-kg mass from the top of the ramp.
Determine the horizontal range of the 5.0-kg mass from the base of the ramp.
25. Two blocks are connected by a “massless” string over a “frictionless” pulley as shown in the diagram.
a)
b)
c)
Determine the acceleration of the blocks.
Calculate the tension in the string .
If the string broke, for what minimum value of
the coefficient of static friction would the 2.0-kg
block not begin to slide?
26. A boy pulls a toy train (consisting of an
engine and a caboose) along a rough floor,
exerting 2.00 N of force as indicated in
the diagram. A frictional force of 0.60 N
acts on the engine and a frictional force of
0.40 N acts on the caboose.
a)
b)
c)
Draw free-body diagrams of both the engine and caboose.
Determine the acceleration of the entire train.
Calculate the tension in the string between the engine and the caboose.
27. Answer one of the following two questions:
a)
b)
5 kg
tension?
Examine the setup in the diagram. The mass of
the uniform bar is 25 kg, and it is 2.0 m long.
What is the tension required in the string to provide static
equilibrium? (3 mks)
1.5 m
The two (2) masses are suspended by ideal wires over
pulleys. They join in the centre to support an 18 kg mass in
static equilibrium. What is the angle of declination (θ) for
each string? (3 mks)
θ
15 kg
15 kg
18 kg
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