Deck 8: Rotational Motion

Question 1

Which of these animals has a quicker stride?

A)giraffe
B)horse
C)cat
D)mouse

Answer 1

mouse

Question 2

You can swing your legs to and fro more frequently when your legs are

A)straight.
B)bent.
C)same either way

Answer 2

bent.

Question 3

The circumference of a bicycle wheel is 2 meters. If it rotates at 1 revolution per second then its linear speed is

A)1 m/s.
B)2 m/s.
C)3 m/s.
D)3)14 m/s.
E)6.28 m/s.

Answer 3

2 m/s.

Question 4

A tightrope walker more easily balances on a tight wire if her pole

A)is held high.
B)droops.
C)is short but heavy.

Question 5

When a train makes a curve, a tapered wheel rim is able to

A)cover different distances per revolution.
B)maintain a fixed rotational speed.
C)reduce differences in angular speeds.

Question 6

If a turntable's rotational speed is doubled, then the linear speed of a pet hamster sitting on the edge of the record will

A)double.
B)halve.
C)remain the same.

Question 7

Each rolling wheel of a railroad train is tapered. Compared with the wide part, the narrow part of the wheel has a tangential speed that is

A)less.
B)greater.
C)the same for both.

Question 8

Your pet hamster sits on a record player that has constant angular speed. If the hamster moves to a point twice as far from the center, then its linear speed

A)doubles.
B)halves.
C)remains the same.

Question 9

The tapered shape of the wheel rims that ride on railroad tracks allows opposite wheels to

A)in effect, vary their diameters.
B)travel at different linear speeds for the same rotational speed.
C)both of these
D)none of these

Question 10

Consider two flywheels of the same size and shape, but one with twice the mass. Rotational inertia of the more massive one is

A)two times greater.
B)four times greater.
C)the same as the other one.
D)half.

Question 11

The rotational inertia of your leg is greater when your leg is

A)straight.
B)bent.
C)same either way

Question 12

If you're on a Ferris wheel at a carnival, seated 10 m from the Ferris wheel's axis that makes a complete rotation each minute, your linear speed is

A)10 m/min.
B)31.4 m/min.
C)62.8 m/min.
D)100 m/min.
E)need more information

Question 13

When railroad tracks make a curve, the outer track is longer. This means a wheel that rides on the outer track needs to somehow

A)roll slower than the wheel on the inner track.
B)maintain the same speed as the wheel on the inner track.
C)roll faster than the wheel on the inner track.

Question 14

The rotational inertia of a pencil is greatest about an axis

A)along its length, where the lead is.
B)about its midpoint, like a propeller.
C)about its end, like a pendulum.

Question 15

An industrial flywheel has a greater rotational inertia when most of its mass is

A)nearer the rim.
B)nearer the axis.
C)uniformly spread out as in a disk.

Question 16

The net force exerted on a car traveling in a circular path at constant speed is

A)directed forward, in the direction of travel.
B)directed toward the center of the curve.
C)zero because the car is not accelerating.
D)none of the above

Question 17

Which horse moves faster in m/s on a merry-go-round?

A)one near inner rail
B)one near outer rail
C)both move at the same speed in m/s.

Question 18

Horses with the greatest linear speed on a merry-go-round are located

A)near the center.
B)near the outside.
C)anywhere, because they all move at the same speed.

Question 19

A flywheel's diameter is twice that of another of the same shape and mass. Rotational inertia of the larger flywheel is

A)two times greater.
B)four times greater.
C)the same as the other's.
D)half.

Question 20

Consider a string with several rocks tied along its length at equally spaced intervals. You whirl the string overhead so that the rocks follow circular paths. Compared with a rock at the end of the string, a rock at the middle moves

A)half as fast.
B)twice as fast.
C)at the same linear speed.

Question 21

Compared with a force, a torque involves

A)rotation.
B)leverage.
C)distance from an axis of rotation.
D)all the above

Question 22

Which jar will roll down an incline in the shortest time, an empty one or one filled with peanut butter?

A)the empty jar
B)both reach the bottom at the same time
C)the filled jar
D)need more information

Question 23

A ring, a disk, and a solid sphere begin rolling down a hill together. Which reaches the bottom first?

A)ring
B)disk
C)sphere
D)all reach the bottom at the same time
E)need more information

Question 24

Which tin can will roll down an incline in the shortest time, one filled with water or one filled with ice? (Hint: water 'slides' inside the can.)

A)with water
B)with ice
C)both the same
D)need more information

Question 25

A torque acting on an object tends to produce

A)equilibrium.
B)rotation.
C)linear motion.
D)velocity.
E)a center of gravity.

Question 26

Stand a broom upright on the end of its pole and let it topple to the floor. Repeat, but with the bristles end on the floor. The faster fall will be the broom standing on its

A)pole-end.
B)bristles-end.
C)the same either way.

Question 27

Stand a broom upright on the end of its pole and let it topple to the floor. Repeat, but with the bristles end on the floor. The faster fall will be the broom standing on its

A)pole-end.
B)bristles-end.
C)the same either way

Question 28

To rotate a stubborn screw, it is best to use a screwdriver that has a

A)wide handle.
B)long handle.
C)smooth handle.
D)none of the above

Question 29

On a balanced seesaw, a boy three times as heavy as his partner sits

A)less than 1/3 the distance from the fulcrum.
B)1/3 the distance from the fulcrum.
C)more than 1/3 the distance from the fulcrum.

Question 30

If Alex wishes to rotate his skateboard, then he must apply a

A)torque.
B)rotational maneuver.
C)pause before bearing down on the board.

Question 31

Stand a meterstick on its end and let it rotate to the floor. If you attach a heavy glob of clay to its upper end and repeat, the time to fall will be

A)shorter.
B)longer.
C)the same.

Question 32

A ball that gains speed as it rolls down a hill experiences a

A)net torque.
B)net force.
C)both of these
D)neither of these

Question 33

Two people are balanced on a seesaw. If one person leans inward toward the center of the seesaw, that person's end of the seesaw tends to

A)rise.
B)fall.
C)stay at the same level.
D)need more information

Question 34

A vertically-held sledge hammer is easier to balance when the heavier end is

A)on your hand.
B)at the top, away from your hand.
C)same either way

Question 35

If you place a pipe over the end of a wrench when trying to rotate a stubborn bolt, effectively making the wrench handle twice as long, you'll multiply the torque by

A)two.
B)four.
C)eight.

Question 36

A ring and a disk both at rest roll down a hill together. Which rolls slower?

A)ring
B)disk
C)depends on the masses
D)both roll at the same speed
E)need more information

Question 37

For a system in mechanical equilibrium, the resultant

A)force must be zero.
B)torque must be zero.
C)both of these
D)none of these

Question 38

A coin and a ring roll down an incline at the same time. The one to first reach the bottom is the

A)ring.
B)coin.
C)both reach the bottom at the same time

Question 39

A vertically-held sledge hammer is easier to balance when the heavier end is

A)on your hand.
B)at the top, away from your hand.
C)the same either way

Question 40

A ball gains speed while rolling down a hill due mainly to

A)its rotational inertia.
B)its angular acceleration.
C)a balanced torque.
D)an unbalanced torque.

Question 41

You can safely stand on the overhanging end of a heavy plank that rests on a table. How much overhang depends on your mass and the mass of the plank. If you can stand on the end of a plank that overhangs the edge of the supporting table 1/5 its total length, how massive is the plank compared to your mass?

A)1/3
B)the same
C)2/3
D)1 and 1/3 times
E)more than 1 and 1/3 times

Question 42

Centrifugal forces are an apparent reality to observers in a reference frame that is

A)moving at constant velocity.
B)an inertial reference frame.
C)at rest.
D)rotating.
E)none of the above

Question 43

If Earth rotated more slowly about its axis, your weight would

A)increase.
B)decrease.
C)stay the same.
D)be zero.

Question 44

You can safely stand on the overhanging end of a heavy plank that rests on a table. How much overhang depends on your mass and the plank's mass. If you can stand on the end of a plank that overhangs the edge of the supporting table 1/4 its total length, how massive is the plank compared to your mass?

A)1/2
B)the same
C)1 and 1/2 times
D)twice
E)4 times

Question 45

The center of mass of a human body is located at a point that

A)is fixed, but different for different people.
B)is always directly behind the belly button.
C)changes as a person bends over.
D)none of the above

Question 46

The long, heavy tail of a spider monkey enables the monkey to easily vary its

A)weight.
B)momentum.
C)inertia.
D)center of gravity.
E)none of the above

Question 47

A 1-kg rock is suspended from the tip of a horizontal meterstick at the 0-cm mark so that the meterstick barely balances like a seesaw when its fulcrum is at the 12.5-cm mark. From this information, the mass of the meterstick is

A)1/4 kg.
B)1/2 kg.
C)3/4 kg.
D)1 kg.
E)none of the above

Question 48

Which of these has its center of mass where no mass exists?

A)baseball
B)golf ball
C)basketball
D)none of the above

Question 49

Strictly speaking, to weigh less in the Northern Hemisphere, you should move to a location farther

A)north (toward the pole).
B)south (toward the equator).
C)east.
D)west.

Question 50

Toss a baseball bat into the air and it wobbles about its

A)geometrical center.
B)center of mass.
C)heavier end.

Question 51

If you balance a broom horizontally on one finger, the center of gravity of the broom will be above your finger, closer to the bristles end than the handle end. If you saw the broom in two pieces at that point and weigh the two parts on a scale, you'll find that the heavier part is the

A)bristles part.
B)handle part.
C)both the same weight

Question 52

A solitary boy cannot balance on a seesaw with its fulcrum at its midpoint. If the fulcrum is moved to one-quarter the distance from the boy, balance is achieved when the weight of the boy is

A)less than the weight of the seesaw.
B)equal to the weight of the seesaw.
C)more than the weight of the seesaw.
D)need more information

Question 53

If Earth had a pair of identical moons on opposite sides of the same circular orbit, the center of gravity of the double-moon-Earth system would be

A)inside the Earth, but off center.
B)at the center of the Earth.
C)outside the Earth, but within the orbital path of the moons.
D)outside the Earth, but beyond the orbital path of the moons.

Question 54

A boy plays solitary seesaw by placing the seesaw's fulcrum one-eighth the distance from where he sits at one end. Which weighs more?

A)the boy
B)the seesaw
C)they have equal weights
D)need more information

Question 55

The main reason a person weighs less at the equator than at the poles involves the

A)spin of the Earth.
B)influence of the Sun, Moon, and all the planets.
C)law of action and reaction.

Question 56

When riding at constant velocity on a Segway electric vehicle, your center of mass is

A)slightly in front of the point between wheels below.
B)slightly behind the point between wheels below.
C)directly above the point between wheels below.

Question 57

The force responsible for a car moving steadily along a no-friction icy banked curve is due to

A)centrifugal effects.
B)the normal force at right angles to the curved surface.
C)the radial component of the normal force.
D)none of the above

Question 58

A 1-kg rock is suspended from the tip of a horizontal meterstick at the 0-cm mark so that the meterstick barely balances like a seesaw when its fulcrum is at the 25-cm mark. From this information, the mass of the meterstick is

A)1/4 kg.
B)1/2 kg.
C)3/4 kg.
D)1 kg.
E)none of the above

Question 59

The famous Leaning Tower of Pisa doesn't topple over because its center of gravity is

A)relatively low for such a tall building.
B)stabilized by its structure.
C)displaced from its center.
D)above a place of support.
E)in the same place as its center of mass.

Question 60

To kick a football so it won't topple end over end, kick it so the force of impact extends

A)above its center of gravity.
B)through its center of gravity.
C)below its center of gravity.

Question 61

As a huge rotating cloud of particles in space gravitate together forming an increasingly dense ball, it shrinks in size and

A)rotates slower.
B)rotates at the same speed.
C)rotates faster.
D)cannot rotate.

Question 62

If the planet Jupiter underwent gravitational collapse, its rate of rotation about its axis would

A)decrease.
B)increase.
C)stay the same.
D)need more information

Question 63

The gravitational field simulated by rotation in a space habitat that is best suited for humans is

A)zero.
B)g.
C)one-quarter g.
D)one-half g.
E)three-quarters g.

Question 64

The bob of a conical pendulum swings in a

A)to-and-fro path.
B)circular path.
C)chaotic path.

Question 65

The chef at the infamous Fattening Tower of Pizza tosses a spinning disk of uncooked pizza dough into the air. The disk becomes wider during its flight, while its rotational speed

A)remains constant.
B)quickens.
C)slows.

Question 66

As the polar icecaps melt, the resulting water spreads over the entire Earth. This new mass distribution tends to make the length of a day

A)longer.
B)shorter.
C)none of these

Question 67

A difference between linear momentum and angular momentum involves

A)a radial distance.
B)two types of speed.
C)both of these
D)neither of these

Question 68

When a twirling ice skater brings her arms inward, her rotational speed

A)decreases.
B)remains the same.
C)increases.

Question 69

A swimming area in a rotating space habitat is located in a region of 1/4 g. If a diver can jump 1 m high in a 1-g region, how high can the same diver jump in the swimming area?

A)1 m
B)2 m
C)4 m
D)16 m
E)more than 16 m

Question 70

Centripetal force does no work on a circularly-moving object because

A)no change in energy occurs.
B)rotational energy transfers to kinetic energy.
C)centripetal force has no component in the direction of motion.
D)none of the above.

Question 71

Multiple the equation for linear momentum by radial distance r and you have

A)rotational kinetic energy.
B)angular momentum.
C)rotational inertia.

Question 72

As you crawl toward the edge of a large freely-rotating horizontal turntable in a carnival funhouse, the angular momentum of you and the turntable

A)decreases.
B)increases.
C)remains the same, but the revolutions per minute decrease.
D)decreases in direct proportion to your decrease in revolutions per minute.
E)none of these

Question 73

If the rotational speed of a rotating habitat in space increases, the weight experienced by occupants

A)decreases.
B)stays the same.
C)increases.
D)is always zero.

Question 74

When you do somersaults, you'll more easily rotate when your body is

A)straight with both arms above your head.
B)straight with both arms at your sides.
C)curled into a ball shape.
D)no difference