Download Circular Motion Pretest

Name: ________________________
Block: ___________________ ID: A
Circular Motion Pretest
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
1. When an object is moving with uniform circular motion, the object’s tangential speed
A) is circular.
B) is perpendicular to the plane of motion.
C) is constant.
D) is directed toward the center of motion.
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2. When an object is moving with uniform circular motion, the centripetal acceleration of the object
A) is circular.
B) is perpendicular to the plane of motion.
C) is zero.
D) is directed toward the center of motion.
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3. What term describes a change in the speed of an object in circular motion?
A) tangential speed
C) centripetal acceleration
B) tangential acceleration
D) centripetal force
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4. What is the term for the net force directed toward the center of an object’s circular path?
A) circular force
C) centripetal force
B) centrifugal force
D) orbital force
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5. Which of the following can be a centripetal force?
A) friction
C) tension
B) gravity
D) all of the above
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6. The centripetal force on an object in circular motion is
A) perpendicular to the plane of the object’s motion.
B) in the plane of the object’s motion and perpendicular to the tangential speed.
C) in the plane of the object’s motion and in the same direction as the tangential speed.
D) in the plane of the object’s motion and in the direction opposite the tangential speed.
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7. The centripetal force on an object in circular motion is
A) in the same direction as the tangential speed.
B) in the direction opposite the tangential speed.
C) in the same direction as the centripetal acceleration.
D) in the direction opposite the centripetal acceleration.
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8. When a car makes a sharp left turn, what causes the passengers to move toward the right side of the car?
A) centripetal acceleration
C) centrifugal force
B) centripetal force
D) inertia
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9. A ball is whirled on a string, then the string breaks. What causes the ball to move off in a straight line?
A) centripetal acceleration
C) centrifugal force
B) centripetal force
D) inertia
1
Name: ________________________
ID: A
____ 10. In this text, which of the following symbols represents the constant of universal gravitation?
A) F g
C) g
B) G
D) F c
____ 11. Which of the following equations expresses Newton’s law of universal gravitation?
mv t 2
mE
A) F c 
C) g  G 2
r
r
m1 m2
m1 m2
B) F g 
D) F g  G 2
r
r
____ 12. When calculating the gravitational force between two extended bodies, you should measure the distance
A) from the closest points on each body.
B) from the most distant points on each body.
C) from the center of each body.
D) from the center of one body to the closest point on the other body.
____ 13. Until the middle of the 16th century, most people believed ____ was at the center of the universe.
A) Earth
C) the sun
B) the moon
D) a black hole
____ 14. The equation for the speed of an object in circular orbit is v t 
equation?
A) the mass of the sun
B) the mass of Earth
G
m
. What does m represent in this
r
C) the mass of the central object
D) the mass of the orbiting object
____ 15. Which of the following quantities measures the ability of a force to rotate or accelerate an object around an
axis?
A) axis of rotation
C) tangential force
B) lever arm
D) torque
____ 16. Where should a force be applied on a lever arm to produce the most torque?
A) closest to the axis of rotation
B) farthest from the axis of rotation
C) in the middle of the lever arm
D) It doesn’t matter where the force is applied.
____ 17. If you want to open a swinging door with the least amount of force, where should you push on the door?
A) close to the hinges
C) as far from the hinges as possible
B) in the middle
D) It does not matter where you push.
____ 18. What kind of simple machine are you using if you pry a nail from a board with the back of a hammer?
A) a wedge
C) a lever
B) a pulley
D) a screw
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Name: ________________________
ID: A
____ 19. Horses that move with the fastest linear speed on a merry-go-round are located
A) on the outside
C) toward the center
B) in the middle
D) all go the same speed
____ 20. A broom is easier to balance on its end when the heavier end (the brush end) is
A) closer to your hand
C) halfway between your hand and the end
B) further from your hand
D) it doesn’t matter where, you can’t balance
a broom on its end.
____ 21. A torque acting on an object tends to produce
A) rotation
B) equilibrium
C) velocity
D) linear motion
____ 22. To turn a stubborn screw, it is best to use a screwdriver that has a
A) wide handle
C) smooth handle
B) long handle
D) none of these
____ 23. A small boy places a rock under the middle of a of a long wood plank, sits near one end and his mother sits
near the opposite end. To balance each other
A) the mother should move further away
C) both should move closer to the ends of the
from the boy.
plank.
B) the boy should move further away from
D) both should move closer to the middle of
his mother.
the plank.
____ 24. When swinging a yoyo in a vertical loop, where would the tension force be the greatest?
A) at the top
C) on the downward side
B) at the bottom
D) on the upward side
____ 25. When swinging a yoyo in a horizontal loop, where would the tension force be the greatest?
A) when it is going away from your head
C) when you just start swinging
B) when it is going toward your head
D) once you get to constant speed, the tension
force is the same everywhere in the loop
____ 26. When swinging a yoyo in a horizontal loop, when would the tension force be the greatest?
A) when you have a short string going slowly C) when you have a long string going slowly
B) when you have a short string going fast
D) when you have a long string going quickly
A child rides a bicycle in a circular path with a radius of 2.0 m. The tangential speed of the bicycle is 2.0 m/s.
The combined mass of the bicycle and the child is 43 kg.
____ 27. What kind of force provides the centripetal force on the bicycle?
A) gravitational force
C) air resistance
B) friction
D) normal force
____ 28. Why does an astronaut weigh less on the moon than on Earth?
A) The astronaut has less mass on the moon.
B) The astronaut is farther from Earth’s center when he or she is on the moon.
C) The gravitational field strength is less on the moon’s surface than on Earth’s surface.
D) The astronaut is continually in free fall because the moon orbits Earth.
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Name: ________________________
ID: A
____ 29. The gravitational force between two masses is 36 N. What is the gravitational force if the distance between
them is tripled? (G = 6.673  10 11 Nm2 /kg 2 )
A) 4.0 N
C) 18 N
B) 9.0 N
D) 27 N
____ 30. Two small masses that are 10.0 cm apart attract each other with a force of 10.0 N. When they are 5.0 cm
apart, these masses will attract each other with what force?
(G = 6.673  10 11 Nm2 /kg 2 )
A) 5.0 N
C) 20.0 N
B) 2.5 N
D) 40.0 N
____ 31. How would the speed of Earth’s orbit around the sun change if Earth’s distance from the sun increased by 4
times?
A) It would increase by a factor of 2.
C) It would decrease by a factor of 2.
B) It would increase by a factor of 4.
D) The speed would not change.
____ 32. How would the speed of Earth’s orbit around the sun change if Earth’s mass increased by 4 times?
A) It would increase by a factor of 2.
C) It would decrease by a factor of 2.
B) It would increase by a factor of 4.
D) The speed would not change.
____ 33. When an astronaut in orbit experiences apparent weightlessness,
A) no forces act on the astronaut.
B) no gravitational forces act on the astronaut.
C) the net gravitational force on the astronaut is zero.
D) the net gravitational force on the astronaut is not balanced by a normal force.
____ 34. If you cannot exert enough force to loosen a bolt with a wrench, which of the following should you do?
A) Use a wrench with a longer handle.
B) Tie a rope to the end of the wrench and pull on the rope.
C) Use a wrench with a shorter handle.
D) You should exert a force on the wrench closer to the bolt.
____ 35. Suppose a doorknob is placed at the center of a door. Compared with a door whose knob is located at the edge,
what amount of force must be applied to this door to produce the torque exerted on the other door?
A) one-half as much
C) one-fourth as much
B) two times as much
D) four times as much
____ 36. On a balanced seesaw, a boy three times as heavy as his partner sits
A) 3 times as far away from fulcrum
C) Closer than 1/3 from the fulcrum
B) 1/3 as far away from the fulcrum
D) Farther than 3 times from the fulcrum.
____ 37. Put a pipe over the end of a wrench when trying to turn a stubborn nut on a bolt, to effectively make the wrench
handle twice as long, you'll multiply the torque by
A) two
C) 1/2
B) four
D) 1/4
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Name: ________________________
____ 38. For a system in equilibrium
A) the resultant force must be zero.
B) the resultant torques must be zero.
ID: A
C) the resultant forces and torques must both
be zero.
D) the resultant forces and torques must be
equal.
____ 39. Two people are balanced on a seesaw. If one person leans toward the center of the seesaw, that person's end of
the seesaw will
A) rise
C) rise then fall
B) fall
D) stay at the same level
____ 40. Where in a vertical loop in a roller coaster would a rider feel the lightest?
A) at the top
C) on the upward side
B) at the bottom
D) on the downward side
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ID: A
Circular Motion Pretest
Answer Section
MULTIPLE CHOICE
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7-1.1
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7-2.2
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7-3.1
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7-4.1
7-4.1
7-4.1
7-4.3
OBJ: 7-1.2
OBJ: 7-2.1
ID: A
29. ANS: A
Given
F 1 = 36 N
r 2 = 3r 1
G = 6.673  10 11 Nm2 /kg 2
Solution
r 2  3r 1
F1  G
F2  G
F2 
1
9
m1 m2
r1 2
m1 m2
r2
2
 36 N
G
m1 m2
 3r 
 1
G
2
m1 m2
9r 1
2

1
9
G
m1 m2
r1
2

1
9
F1
36 N  4.0 N
PTS: 1
30. ANS: D
Given
F 1  10.0 N
DIF: II
OBJ: 7-2.2
r 1  10.0 cm
r 2  5.0 cm
G  6.673  10 11 Nm2 / kg 2
Solution
r2
5.0 cm
1


r 1 10.0 cm 2
1
r 2  2 r1
F1  G
F2  G
m1 m2
r1 2
m1 m2
 r 
 2
2
 10.0 N
G
m1 m2
 1 
 r 1 
 2 
2
G
m1 m2
1
r 2
4 1
 4G
m1 m2
r1 2
 4F 1
F 2  (4) 10.0 N  40.0 N
PTS: 1
DIF: II
OBJ: 7-2.2
2
ID: A
31. ANS: C
Given
r 2  4r 1
Solution
vt1 
G
vt2 
G
vt2
vt1
m
r1
m
4r 1
m
G
4r 1

G
vt2 
1

1
2
4
m

1
2
r1
v t 1 , i.e., speed would decrease by a factor of 2
PTS: 1
32. ANS: A
DIF: II
OBJ: 7-3.3
Given
m2  4mE
Solution
vt1 
G
vt2 
G
vt2
vt1
mE
r1
4mE
r1
G

(4mE )
r1
mE
G r
1

4 2
v t 2  2v t 1 , i.e., speed would increase by a factor of 2
PTS: 1
DIF: II
OBJ: 7-3.3
3
ID: A
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OBJ: 7-3.3
OBJ: 7-4.1
OBJ: 7-4.2