Download File - SPH3U- 11 University Prep Physics

SPH3U Forces Unit Test
Name:
Date:
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
1. Which of the following fundamental forces is the weakest?
a. gravitational
d. strong nuclear
b. electromagnetic
e. They are equally strong.
c. weak nuclear
____
2. A curling stone is pushed along the ice surface during its delivery. Which of the following free-body diagrams
best represents the curling stone?
a. A
b. B
c. C
____
3. A hockey puck slides along an ice surface shortly after it has left the hockey stick that propelled it. Which of
the following free-body diagrams best represents the hockey puck?
a. A
b. B
c. C
____
d. D
e. E
d. D
e. E
4.Study the free-body diagram below and determine what additional force(s) would be required for the object to achieve
uniform motion.
a. 1 N [W]
b. 1 N [E]
c. 2 N [N] and 1 N [W]
____
5. The free-body diagram below represents a 2000-kg elevator. What is the motion of the elevator if the tension
in the cable is 1.96  104 N? (Assume 3 significant digits.)
a.
b.
c.
d.
e.
____
The elevator might be accelerating upward.
The elevator might be accelerating downward.
The elevator must be accelerating.
The elevator cannot be undergoing uniform motion.
The elevator must not be accelerating.
6. The free-body diagram of a 4.0-kg object is shown below. What additional force must act so that the object
has an acceleration of 2.5 m/s2 [W]?
a. 14.0 N [W]
b. 10.0 N [W]
c. 8.0 N [W]
____
d. 2 N [S] and 1 N [E]
e. 2 N [S] and 1 N [W]
d. 6.0 N [W]
e. 4.0 N [W]
7. If you weighed 112 N on the Moon where g = 1.6 N/kg, how much would you weigh on Earth?
a. 1.1  102 N
d. 1.1  104 N
4
b. 1.7  10 N
e. 6.9  103 N
c. 6.9  102 N
____
8. The value of "g" at the surface of Mars is 3.7 N/kg. How much would a 60.0-kg person weigh at an altitude
above the Martian surface equivalent to the planet's radius?
a. 2.2  102 N
d. 56 N
2
b. 1.6  10 N
e. 28 N
c. 1.1  102 N
____
9. If Earth was twice its present mass, but its size was not changed, you would weigh
a. half as much
d. one-quarter as much
b. twice as much
e. the same amount
c. four times as much
____ 10. What would the gravitational field strength be on a planet with twice Earth's mass and twice its radius?
a. 78.4 N/kg
d. 9.8 N/kg
b. 39.2 N/kg
e. 4.9 N/kg
c. 19.6 N/kg
____ 11. Which of the following statements concerning gravitational fields is true?
a. The strength of an object's gravitational field varies inversely as the square of the distance
to its centre.
b. The strength of an object's gravitational field varies directly as the square of its mass.
c. The Moon's gravitational field is much smaller than Earth's because the Moon's radius is
so much smaller than Earth's.
d. An object's mass alone dictates the strength of the gravitational field at its surface.
e. An object's size alone dictates the strength of its gravitational field.
____ 12. Which of the fundamental forces is directly responsible for frictional forces?
a. strong nuclear force
d. electromagnetic force
b. weak nuclear force
e. a combination of all forces
c. gravitational force
____ 13. The coefficient of friction stems from the
a. nature of the two surfaces in contact
b. mass of the object
c. strength of the applied force
d. strength of the normal force
e. strength of the gravitational force
____ 14. If all other forces can be ignored and the strength of the frictional force is greater than the applied force and
oppositely directed, the object
a. could be speeding up or slowing down
b. must be speeding up
c. must be slowing down
d. could be moving with uniform motion
e. could be stopped
Short Answer
15. Define "inertia".
16. Give an example that clearly illustrates Newton's second law.
17. What exactly is a "newton" of force? Give an example of something that would exert a force of one newton.
18. All forces act "by" something and act "on" something. The system diagram below illustrates a crate being
pushed across a floor by a person. FA is the force exerted by the person on the crate. What do the other forces
represent?
19. The gravitational force that the Sun exerts on the planets is responsible for their orbits. Do the planets have a
noticeable gravitational effect on the Sun? What might a very distant observer notice about the Sun if such an
effect is large enough?
20. Provide examples that illustrate that friction is sometimes desirable and sometimes undesirable.
Problem
21. A stationary box of mass 4.2 kg is given a push of 8.2 N [S] along a surface where the frictional force acting
is 5.8 N [N]. The push lasts for 3.6 s and then the box is allowed to slide on its own until it comes to rest.
(a) Draw free-body diagrams to show the box being pushed and sliding on its own.
(b) Determine the acceleration of the box as it is being pushed.
(c) Calculate the speed of the box just as the push ceases.
(d) Determine the acceleration of the box as it is sliding on its own.
22. A wagon of mass 2.4 kg is pushed along the ground at 1.2 m/s2 against a frictional force of 1.22 N. What is
the applied force that is acting? Draw a free-body diagram.
23.A hockey puck of mass 200 g slides along the ice with a speed of 1.2 m/s when it reaches a rough section where the
coefficient of kinetic friction is 0.25. How long will it take the puck to stop sliding? Include a free-body
diagram. (Assume 2 significant digits.)
24.A box of mass 4.5 kg is pushed across a rough surface (K = 0.18) for a distance of 2.0 m by a constant force of 10 N.
If the object reaches a speed of 2.0 m/s by the end of the push, what was its speed at the beginning of the
push? (Assume 2 significant digits.)
25.Show that an applied force of 4.0 N is insufficient to get a stationary 2.0-kg object to move horizontally if the
coefficient of starting friction is 0.25.
SPH3U Forces Unit Test
Answer Section
MULTIPLE CHOICE
1. ANS:
STA:
2. ANS:
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3. ANS:
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4. ANS:
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5. ANS:
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6. ANS:
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7. ANS:
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8. ANS:
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9. ANS:
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10. ANS:
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11. ANS:
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12. ANS:
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13. ANS:
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14. ANS:
STA:
A
FM1.04
E
FM2.04
D
FM2.04
E
FM2.04
E
FM2.04
C
FM2.04
C
FM1.05
D
FM1.05
B
FM1.05
E
FM1.05
A
FM1.05
D
FM1.04
A
FM1.01
C
FM1.07
PTS: 1
REF: K/U
OBJ: 2.1
PTS: 1
REF: I
OBJ: 2.2
PTS: 1
REF: I
OBJ: 2.2
PTS: 1
REF: I
OBJ: 2.2
PTS: 1
REF: I
OBJ: 2.2
PTS: 1
REF: I
OBJ: 2.4
PTS: 1
REF: K/U
OBJ: 3.2
PTS: 1
REF: K/U
OBJ: 3.2
PTS: 1
REF: K/U
OBJ: 3.2
PTS: 1
REF: K/U
OBJ: 3.2
PTS: 1
REF: K/U
OBJ: 3.2
PTS: 1
REF: K/U
OBJ: 3.2
PTS: 1
REF: K/U
OBJ: 3.3
PTS: 1
REF: K/U
OBJ: 3.3
SHORT ANSWER
15. ANS:
Inertia is the tendency for an object to stay at rest or continue travelling with uniform motion.
PTS: 1
REF: K/U
OBJ: 2.2
STA: FM1.01
16. ANS:
A wagon accelerates along a sidewalk when the applied force exerted by a child exceeds the frictional force
exerted by the ground that acts in the opposite direction.
PTS: 1
17. ANS:
REF: K/U
OBJ: 2.4
STA: FM1.07
A 1.0-N force is defined as the force which would provide an acceleration of 1.0 m/s2 to a 1.0-kg object. It is
also approximately equal to the force of gravity exerted on a mass of 100 g, or roughly the weight of an
average apple.
PTS: 1
REF: K/U
OBJ: 2.1
STA: FM1.01
18. ANS:
FN represents the vertical normal force acting by the floor on the crate.
Fg represents the vertical gravitational force exerted by Earth on the crate.
Ff represents the horizontal frictional force exerted by the floor on the crate.
PTS: 1
REF: K/U
OBJ: 2.1
STA: FM1.06
19. ANS:
Yes. The combined gravitational influence of the planets on the Sun is noticeable, albeit very minute. A
distant observer would see the Sun "wobble" slightly as the planets orbit around it. At times of planetary
alignment, the effect will be the most noticeable.
PTS: 1
REF: K/U
OBJ: 3.2
STA: FM1.05
20. ANS:
Friction is what stops a car when its brake pads are pushed against the wheels' rotors. Friction is undesirable
when you want something to slide as freely as possible, for example, a motor's shaft inside bearings.
PTS: 1
PROBLEM
21. ANS:
(a)
REF: MC
OBJ: 3.3
STA: FM3.02
(b)
The acceleration of the box is 0.57 m/s2 [S].
(c)
The speed of the box is 2.1 m/s.
(d)
The acceleration of the box is 1.4 m/s2 [N].
PTS: 1
REF: I
OBJ: 2.4
22. ANS:
Let [fwd] be "positive" and [bkwd] be "negative".
STA: FM2.04
The applied force is 4.0 N [fwd].
PTS: 1
23. ANS:
REF: I
OBJ: 2.4
STA: FM2.04
The puck will slide for 0.49 s before stopping.
PTS: 1
24. ANS:
REF: I
OBJ: 3.4
STA: FM2.04
The speed at the beginning of the push was 1.8 m/s.
PTS: 1
25. ANS:
REF: I
OBJ: 3.4
STA: FM2.04
Since FA < Ff, the object will not begin to slide.
PTS: 1
REF: I
OBJ: 3.4
STA: FM2.04