Circular and Rotational Motion MCQs

Question 1

A solid sphere of mass 5 kg and radius 0.2 m has I = 25MR^2 =

Accepted Answer

0.08 kg m^2

Answer

0.2 kg m^2

Answer

0.4 kg m^2

Answer

0.04 kg m^2

Question 2

A wheel turns at 60 revolutions per minute. Its angular velocity is:

Accepted Answer

6.28 rad/s

Answer

12.6 rad/s

Answer

1 rad/s

Answer

3.14 rad/s

Question 3

The true weight of an astronaut in orbit is:

Accepted Answer

not zero — gravity still acts on them

Answer

infinite

Answer

equal to their mass

Answer

exactly zero

Question 4

If a satellite's speed were too small for its orbit, it would:

Accepted Answer

spiral or fall towards the Earth

Answer

fly off into space

Answer

stay in the same orbit

Answer

stop in space

Question 5

A wheel starts at 5 rad/s with angular acceleration 0.5 rad/s^2. After 20 s its angular velocity is:

Accepted Answer

15 rad/s

Answer

7.5 rad/s

Answer

30 rad/s

Answer

11 rad/s

Question 6

A bucket of water is swung in a vertical circle of radius 0.4 m. The minimum speed at the top so the water stays in is (g = 9.8 m/s^2):

Accepted Answer

1.98 m/s

Answer

0.99 m/s

Answer

3.96 m/s

Answer

2.8 m/s

Question 7

In uniform circular motion, which quantity is constant?

Accepted Answer

speed

Answer

velocity

Answer

acceleration vector

Answer

momentum vector

Question 8

A disc's angular velocity changes from 10 rad/s to 40 rad/s in 5 s. Its angular acceleration is:

Accepted Answer

6 rad/s^2

Answer

3 rad/s^2

Answer

12 rad/s^2

Answer

-6 rad/s^2

Question 9

A centrifuge tube is 0.15 m from the axis and spins at 6000 rpm. The centripetal acceleration is about how many times g (g = 9.8)?

Accepted Answer

6040 g

Answer

12,100 g

Answer

3020 g

Answer

9.62 g

Question 10

When a cyclist leans into a bend, the inward force comes from:

Accepted Answer

friction on the tyres (with the normal reaction balancing weight)

Answer

the cyclist's muscles pushing outward

Answer

gravity alone

Answer

the bicycle's speed

Question 11

A flywheel stores energy as:

Accepted Answer

rotational kinetic energy

Answer

heat

Answer

chemical energy

Answer

elastic energy

Question 12

A space station is a ring of radius 100 m. To produce artificial gravity of 9.8 m/s^2 at the rim, it must rotate at:

Accepted Answer

0.313 rad/s

Answer

0.626 rad/s

Answer

0.098 rad/s

Answer

0.157 rad/s

Question 13

60^circ expressed in radians is:

Accepted Answer

pi3

Answer

3pi

Answer

2pi3

Answer

pi6

Question 14

A gyroscope keeps its axis pointing in a fixed direction because:

Accepted Answer

its large angular momentum resists changes in direction

Answer

friction holds it

Answer

it has no mass

Answer

gravity is zero

Question 15

An ice skater with I = 2 kg m^2 spins at 10 rad/s, then pulls in her arms so I = 5 kg m^2. Her new angular velocity is:

Accepted Answer

4 rad/s

Answer

8 rad/s

Answer

25 rad/s

Answer

2 rad/s

Question 16

An ice skater with I = 6 kg m^2 spins at 3 rad/s, then pulls in her arms so I = 2 kg m^2. Her new angular velocity is:

Accepted Answer

9 rad/s

Answer

4.5 rad/s

Answer

18 rad/s

Answer

1 rad/s

Question 17

If the radius is doubled at the same speed, the centripetal force becomes:

Accepted Answer

half as large

Answer

twice as large

Answer

4 times as large

Answer

unchanged

Question 18

Angular momentum is conserved when:

Accepted Answer

no external torque acts

Answer

the body is at rest

Answer

no external force acts

Answer

kinetic energy is conserved

Question 19

Cream is separated from milk in a dairy centrifuge because:

Accepted Answer

cream is less dense and stays nearer the axis

Answer

cream is magnetic

Answer

cream boils faster

Answer

cream is denser

Question 20

At the axis of a rotating space station, an astronaut would feel:

Accepted Answer

weightless

Answer

pulled outward strongly

Answer

double gravity

Answer

full Earth gravity

Question 21

The Earth's angular momentum about its axis stays nearly constant because:

Accepted Answer

external torques on it are very small

Answer

it is not rotating

Answer

gravity keeps it constant

Answer

it has no mass

Question 22

A fan running at 30 rad/s is switched off and stops uniformly in 10 s. The number of revolutions it makes while stopping is about:

Accepted Answer

23.9

Answer

4.8

Answer

47.7

Answer

150

Question 23

The ideal banking angle of a curve with r = 100 m for v = 20 m/s (g = 10) satisfies tantheta =

Accepted Answer

0.4

Answer

0.2

Answer

4

Answer

2.5

Question 24

One complete revolution equals:

Accepted Answer

2pi rad

Answer

pi rad

Answer

1 rad

Answer

360 rad

Question 25

180^circ expressed in radians is:

Accepted Answer

pi

Answer

2pi

Answer

3pi

Answer

pi2

Circular and Rotational Motion MCQs — Physics (page 4)

76. A solid sphere of mass 5 kg and radius 0.2 m has I = 25MR^2 =

77. A wheel turns at 60 revolutions per minute. Its angular velocity is:

78. The true weight of an astronaut in orbit is:

79. If a satellite's speed were too small for its orbit, it would:

80. A wheel starts at 5 rad/s with angular acceleration 0.5 rad/s^2. After 20 s its angular velocity is:

81. A bucket of water is swung in a vertical circle of radius 0.4 m. The minimum speed at the top so the water stays in is (g = 9.8 m/s^2):

82. In uniform circular motion, which quantity is constant?

83. A disc's angular velocity changes from 10 rad/s to 40 rad/s in 5 s. Its angular acceleration is:

84. A centrifuge tube is 0.15 m from the axis and spins at 6000 rpm. The centripetal acceleration is about how many times g (g = 9.8)?

85. When a cyclist leans into a bend, the inward force comes from:

86. A flywheel stores energy as:

87. A space station is a ring of radius 100 m. To produce artificial gravity of 9.8 m/s^2 at the rim, it must rotate at:

88. 60^circ expressed in radians is:

89. A gyroscope keeps its axis pointing in a fixed direction because:

90. An ice skater with I = 2 kg m^2 spins at 10 rad/s, then pulls in her arms so I = 5 kg m^2. Her new angular velocity is:

91. An ice skater with I = 6 kg m^2 spins at 3 rad/s, then pulls in her arms so I = 2 kg m^2. Her new angular velocity is:

92. If the radius is doubled at the same speed, the centripetal force becomes:

93. Angular momentum is conserved when:

94. Cream is separated from milk in a dairy centrifuge because:

95. At the axis of a rotating space station, an astronaut would feel:

96. The Earth's angular momentum about its axis stays nearly constant because:

97. A fan running at 30 rad/s is switched off and stops uniformly in 10 s. The number of revolutions it makes while stopping is about:

98. The ideal banking angle of a curve with r = 100 m for v = 20 m/s (g = 10) satisfies tantheta =

99. One complete revolution equals:

100. 180^circ expressed in radians is:

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