Deck 17: Physics of Rotation and Equilibrium

Question 1

A 1-kg rock is suspended from the tip of a meter stick at the 0- cm mark so that the meter stick balances like a see-saw when the fulcrum is at the 25-cm mark. From this information, what is the
Mass of the meter stick?

A) 1/4 kg
B) 1 kg
C) 3/4 kg
D) 1/2 kg
E) more than 1 kg

Answer 1

1 kg

Question 2

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

A) straight with both arms at your sides.
B) straight with both arms above your head.
C) balled up.
D) no difference

Answer 2

balled up.

Question 3

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

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

Answer 3

wide handle.

Question 4

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

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

Question 5

Two people are balanced on a see-saw. If one person leans toward the center of the see-saw, that person's end of the see-saw will

A) rise.
B) fall.
C) rise and then fall.
D) fall and then rise.
E) stay at the same level.

Question 6

A phonograph record player has constant rotational speed. The speed of the record surface relative to the pickup needle is greatest

A) at the beginning of the record.
B) at the end of the record.
C) everywhere, because it has the same speed anywhere on the record.

Question 7

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 to a rock in the middle of the
String, a rock at the outer end moves

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

Question 8

If you replace the wheels and tires of your car with new ones having greater diameters, all of your speedometer readings thereafter will

A) increase
B) decrease.
C) remain the same.

Question 9

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

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

Question 10

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) four.
B) two.
C) eight.

Question 11

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

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

Question 12

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

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

Question 13

A ball rolls down a hill mainly because of

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

Question 14

Consider a rotating donut-shaped space habitat where living quarters are on the inside surface farthest from the axis. If the rotational speed of the habitat increases, the apparent weight of people
Inside

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

Question 15

A person weighs less at the equator than at the poles. The main reason for this has to do with

A) the law of action and reaction.
B) the influence of the sun, moon, and all the planets.
C) the spin of the Earth.
D) the shape of the Earth.
E) both the spin of the Earth and the shape of the Earth.

Question 16

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

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

Question 17

The center of gravity of a circular disk of sheet metal is

A) midway between the center and the outside.
B) two-thirds of the way between the center and the outside.
C) at the center of the disk.
D) impossible to predict without knowing the metal density.

Question 18

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

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

Question 19

Your pet hamster sits on a record player whose angular speed is constant. If he moves to a point twice as far from the center, then his linear speed

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

Question 20

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

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

Question 21

Horses that move with the fastest 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 22

A torque acting on an object tends to produce

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

Question 23

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

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

Question 24

A baseball bat is balanced on a fulcrum. The center of gravity of the bat is located

A) above the fulcrum.
B) closer to the heavy end.
C) closer to the handgrip.

Question 25

Suppose the circumference of a bicycle wheel is 2 meters. If it rotates at 1 revolution per second when you are riding the bicycle, then your speed will be

A) 6.28 m/s.
B) 2 m/s.
C) 3.14 m/s.
D) 1 m/s.
E) 3 m/s.

Question 26

A tightrope walker more easily balances on a tightwire if his pole

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

Question 27

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

A) increases.
B) remains constant.
C) decreases.

Question 28

Which moves faster in m/s on a merry-go-round: a horse on the inside or a horse on the outside near the outer rail?

A) outside horse
B) inside horse
C) Both move at the same speed in m/s.

Question 29

For a system in mechanical equilibrium,

A) the resultant torques must be zero.
B) the resultant forces and torques must both be zero.
C) the resultant forces and torques must be equal.
D) the resultant force must be zero.

Question 30

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

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

Question 31

On a balanced see saw, 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.