Download Circular Motion Centripetal Force MC

Exam
Name___________________________________
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
1) Shown below are the velocity and acceleration vectors for an object in several
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different types of motion. In which case is the object's velocity changing while
its speed is not changing?
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
2) If a satellite moves with constant speed in a perfectly circular orbit around the earth,
what is the direction of the acceleration of the satellite?
A) in the backward direction
B) outward away from the earth
C) in the forward direction
D) inward toward the earth
E) The acceleration is zero because the speed is constant.
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3) An object moves in a circular path at a constant speed. Compare the direction of the
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object's velocity and acceleration vectors.
A) Both vectors point in the same direction.
B) The vectors are perpendicular to each other.
C) The vectors point in opposite directions.
D) The acceleration is zero but the velocity is constant.
4)
The Moon is accelerated toward the earth, so it is gradually getting closer to the earth.
A) True
B) False
C) The moon is not accelerated toward the earth.
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5) You are making a circular turn in your car on a horizontal road when you hit a big patch
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of ice, causing the force of friction between the tires and the road to become zero.
While the car is on the ice, it
A) moves along a path that is neither straight nor circular.
B) moves along a straight-line path away from the center of the circle.
C) continues to follow a circular path, but with a radius larger than the original radius.
D) moves along a straight-line path toward the center of the circle.
E) moves along a straight-line path in its original direction.
6) When a car goes around a circular curve on a horizontal road at constant speed, what
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force causes it to follow the circular path?
A) the friction force exerted by the road on the car
B) the normal force exerted on the car by the road perpendicular to the road
C) the force that Earth exerts on the car
D) No force causes the car to do this because the car is traveling at constant speed and
therefore has no acceleration.
7) A car goes around a circular curve on a horizontal road at constant speed. What is the
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direction of the friction force exerted on the car by the road?
A) perpendicular to the curve outward
B) tangent to the curve in the forward direction
C) perpendicular to the curve inward
D) tangent to the curve opposite to the direction of the car's motion
E) There is no friction on the car because its speed is constant.
8)
When an object moves in uniform circular motion, the direction of its acceleration is
A) in the opposite direction of its velocity vector.
B) in the same direction as its velocity vector.
C) depends on the speed of the object.
D) is directed away from the center of its circular path.
E) is directed toward the center of its circular path.
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9) If you swing a bucket of water fast enough in a vertical circle, at the highest point the
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water does not spill out. This happens because an outward force balances the pull of
Earth on the water.
A) True
B) False
10) When a car goes around a banked circular curve at the proper speed for the banking
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angle, what force cause it to follow the circular path?
A) the friction force exerted by the road on the car
B) the normal force exerted by the road on the car perpendicular to the road's surface
C) the force that Earth exerts on the car
D) No force causes the car to do this because the car is traveling at constant speed and
therefore has no acceleration.
11) Two cars go around a banked curve at the proper speed for the banking angle. One car
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has tires with excellent traction, while the other car has bald slippery tires. Which of
these cars is more likely to slide on the pavement as it goes around the curve?
A) the car with the new tires
B) the car with the bald tires
C) Neither car will slide.
D) It depends on if the pavement is wet or dry.
12) Two small balls, A and B, attract each other gravitationally, exerting a force of
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magnitude F on each other. If we now double both masses and the separation of the
balls, what will now be the magnitude of the attractive force that they exert on each
one?
A) 4F
B) 8F
C) F/4
D) 16F
E) F
13) Two small objects, with masses m and M, are originally a distance r apart, and the
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magnitude of the gravitational force they exert on each one is F. The masses are
changed to 2m and 2M, and the distance is changed to 4r. What is the magnitude of the
new gravitational force?
A) 4F
B) 16F
C) F/2
D) F/4
E) F/16
14) Two small objects, with masses m and M, are originally a distance r apart, and the
gravitational force that they exert on each other has magnitude F. The second object
has its mass changed to 2M, and the distance is changed to r/4. What is the magnitude
of the new gravitational force?
A) 16F
B) F/32
C) 2F
D) F/16
E) 32F
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15) A spaceship is traveling to the Moon. At what point is there no more gravitational
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force exerted on it by Earth?
A) when it is half-way there
B) when it gets above the atmosphere
C) when it is closer to the Moon than it is to Earth
D) There is no point where there is no more gravitational force exerted on the
spaceship by Earth
16) If you stood on a planet having a mass four times that of Earth's mass, and a radius two
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times that of Earth's radius, the gravitational force that the planet exerts on you would
be
A) four times more than Earth exerts on you.
B) two times less than Earth exerts on you.
C) two times more than Earth exerts on you.
D) the same as Earth exerts on you.
17) A satellite encircles Mars at a distance above its surface equal to 3 times the radius of
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Mars. If gm is the free-fall acceleration at the surface of Mars, what is the free-fall
acceleration at the location of the satellite?
A) gm/16
B) 0
C) gm/9
D) gm
E) gm/3
18) A hypothetical planet has a mass of one-half that of the earth and a radius of twice that
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of the earth. What is the free-fall acceleration on the planet in terms of g, the free-fall
acceleration at the surface of the earth?
A) g/16
B) g/4
C) g/2
D) g
E) g/8
19) The free-fall acceleration on Planet A is one-sixth what it is on Planet B, and the radius
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of the Planet A is one-fourth that of Planet B. The mass of Planet A is what fraction of
the mass of Planet B?
A) 1/12
B) 1/6
C) 1/24
D) 1/96
E) 1/16
20) Two planets have the same free-fall acceleration on the surface, but planet B has twice
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the radius of planet A. If planet A has mass m, what is the mass of planet B?
A) m/ 2
B) m
C) m/4
D) 4m
E) m 2
21) Two planets have the same free-fall acceleration on the surface, but planet B has twice
the mass of planet A. If planet A has radius r, what is the radius of planet B?
A) 4r
B) r 2
C) r
D) r/ 2
E) 2r
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22) Planet A has twice the mass of Planet B. From this information, what can we conclude
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about the free-fall acceleration at the surface of Planet A compared to that at the surface
of Planet B?
A) The free-fall acceleration on Planet A is greater than the free-fall acceleration on
Planet B, but we cannot say how much greater.
B) The free-fall acceleration on Planet A must be twice as great as the free-fall
acceleration on Planet B.
C) The free-fall acceleration on Planet A must be four times as great as the free-fall
acceleration on Planet B.
D) The free-fall acceleration on Planet A is the same as the free-fall acceleration on
Planet B.
E) We cannot conclude anything about the free-fall acceleration on Planet A without
knowing the radii of the two planets.
23) The
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24) If Earth had twice its present mass but it orbited at the same distance from the sun as it
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reason an astronaut in an Earth satellite feels weightless is that
A) the astronaut is in the state of free fall.
B) the astronaut is at a point in space where the effects of the Moon's gravity and
Earth's gravity cancel.
C) the astronaut's acceleration is zero.
D) this is a psychological effect associated with rapid motion.
E) the astronaut is beyond the range of the earth's gravitational pull.
does now, its orbital period would be
A) 2 years.
B) 3 years.
C) 6 months.
D) 4 years.
E) 1 year.
25) Satellite A has twice the mass of satellite B, and moves at the same orbital distance
from Earth as satellite B. Compare the speeds of the two satellites.
A) The speed of B is equal to the speed of A.
B) The speed of B is one-half the speed of A.
C) The speed of B is four times the speed of A.
D) The speed of B is twice the speed of A.
E) The speed of B is one-fourth the speed of A.
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26) Suppose our sun had 4 times its present mass but the earth orbited it at the same
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distance as it presently does. What would be the length of the year on the earth under
those conditions?
A) four times as long as the present year
B) the same as the present year
C) 1/2 as long as the present year
D) 1/4 as long as the present year
E) twice as long as the present year
27) Halley's Comet is in a highly elliptical orbit around the sun. Therefore the orbital speed
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of Halley's Comet, while traveling around the sun,
A) is constant.
B) is zero at two points in the orbit.
C) decreases as it nears the Sun.
D) increases as it nears the Sun.
28) Let the orbital radius of a planet be R and let the orbital period of the planet be T. What
quantity is constant for all planets orbiting the sun, assuming circular orbits?
A) T3/R2
B) T/R
C) T2/R
D) T/R2
E) T2/R3
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Answer Key
Testname:
1) D
2) D
3) B
4) B
5) E
6) A
7) C
8) E
9) B
10) B
11) C
12) E
13) D
14) E
15) D
16) D
17) A
18) E
19) D
20) D
21) B
22) E
23) A
24) E
25) A
26) C
27) D
28) E
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