True/False
Indicate whether the
sentence or statement is true or false.
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1. |
A
body in uniform circular motion experiences acceleration that is constant
in magnitude.
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2. |
Centripetal acceleration is in a direction tangential to the path
of the object in motion.
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3. |
At
a constant speed, the centripetal acceleration of an object in uniform
circular motion is inversely proportional to the orbital radius, yet,
at a constant period of revolution, the centripetal acceleration is
directly proportional to the orbital radius.
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4. |
The
centrifugal force on an object in uniform circular motion is, as required
by Newton’s first law of motion, directed toward the centre of
the circle.
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5. |
Centripetal force is a fundamental force of nature that applies
to all objects, both natural and human-made, in circular motion.
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6. |
It
is possible for static friction to be the sole force producing centripetal
acceleration in a moving object.
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7. |
The
centripetal and centrifugal forces are an action-reaction pair of forces
for an object in uniform circular motion.
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8. |
Perturbations in the orbits of planets or other heavenly bodies
can be used to locate additional such bodies.
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9. |
The
magnitude of your weight, as calculated from F = mg, yields a
much smaller value than the magnitude of the force of gravity between
you and Earth, as calculated from  .
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10. |
The
International Space Station is an example of an artificial satellite.
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11. |
As
the radius of the orbit of a satellite in uniform circular motion around
a central body increases, the speed of the satellite decreases.
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Multiple Choice
Identify
the letter of the choice that best completes the statement or answers
the question.
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12. |
You
are whirling a rubber stopper of mass m, attached to a string,
in a vertical circle at a high constant speed. At the top of the circle,
the net force that causes acceleration is
a. |
horizontal
and greater in magnitude than mg |
b. |
horizontal and lower in magnitude than mg |
c. |
vertically downward and greater in magnitude than
mg |
d. |
vertically downward and lower in magnitude than
mg |
e. |
vertical and equal in magnitude to mg |
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13. |
At
the bottom of the circle for this same rubber stopper, the net force
that causes acceleration is
a. |
horizontal,
and greater in magnitude than mg |
b. |
horizontal, and lower in magnitude than mg |
c. |
vertically upward, and greater in magnitude than
mg |
d. |
vertically upward, and lower in magnitude than
mg |
e. |
vertical, and equal in magnitude to mg |
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14. |
You
now reduce the speed of this stopper, so that the stopper barely makes
it over the top of the circle. When the stopper is at its highest point,
the net force toward the centre of the circle is
a. |
horizontal,
and greater in magnitude than mg |
b. |
horizontal, and lower in magnitude than mg |
c. |
vertically downward, and greater in magnitude than
mg |
d. |
vertically downward, and lower in magnitude than
mg |
e. |
vertical, and equal in magnitude to mg |
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15. |
You
are a passenger in a car making a right turn on level ground. The direction
of the instantaneous velocity is north. The direction of the centrifugal
force you feel is
a. |
west |
b. |
northwest |
c. |
north |
d. |
northeast |
e. |
east |
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For
questions 16 to 19, refer to Figure 1.
Figure 1
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16. |
When
the tip of the minute hand on a clock face is moving past the 4 o’clock
position, the vector in Figure 1(a) that gives the direction
of the acceleration of the tip is
a. |
vector
4 |
b. |
vector
7 |
c. |
vector
1 |
d. |
vector
6 |
e. |
vector
10 |
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17. |
When
the child on the swing in Figure 1(b) reaches the lowest position
on the swing, the vector in Figure 1(a) that gives the direction
of the centripetal force is
a. |
vector
4 |
b. |
vector
10 |
c. |
vector
12 |
d. |
vector
6 |
e. |
vector
8 |
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18. |
In
Figure 1(c), the car is travelling at a constant speed around
a banked curve. The direction of the normal force acting on the car
and the direction of the centripetal acceleration of the car are the
same as the directions, in Figure 1(a), of
a. |
vector 12 and vector 6, respectively |
b. |
vector
11 and vector 7, respectively |
c. |
vector 11 and vector 8, respectively |
d. |
vector
11 and vector 9, respectively |
e. |
vector 11 and vector 11, respectively |
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19. |
At
the instant shown in Figure 1(d), the skier is travelling over
a frictionless, circular hump. The direction of the skier’s instantaneous
velocity and the direction of the net force acting on the skier are
the same as the directions, in Figure 1(a), of
a. |
vector
9 and vector 9, respectively |
b. |
vector 9 and vector 6, respectively |
c. |
vector
10 and vector 7, respectively |
d. |
vector 8 and vector 5, respectively |
e. |
vector
8 and vector 12, respectively |
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For
questions 20 to 23, refer to Figure 2.
Figure 2
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20. |
Choose
the graph in Figure 2 that most accurately represents the variation
in the net force toward the centre of the circle on an object in uniform
circular motion, as a function of the mass of the object.
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21. |
Choose
the graph in Figure 2 that most accurately represents the variation
in the gravitational force of attraction between two uniform spheres,
as a function of their centre-to-centre separation.
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22. |
Choose
the graph in Figure 2 that most accurately represents the variation
in the centripetal acceleration of an object in uniform circular motion,
as a function of the speed of the object at a constant radius.
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23. |
Choose
the graph in Figure 2 that most accurately represents the variation
in the speed of a moon undergoing uniform circular motion around a planet,
as a function of the mass of the planet.
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