Chapter 8 Physics

1 kg

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 seesaw when the fulcrum is at the 25-cm mark. From this information, what is the mass of the meter stick?

an unbalanced torque.

A ball rolls down a hill mainly because of

above the fulcrum

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

directed toward the center of the curve

A car travels in a circle with constant speed. The net force on the car is

rotates faster.

A huge rotating cloud of particles in space gravitate together to form an increasingly dense ball. As it shrinks in size, the cloud

L = 760 kg⋅m2s

Calculate the angular momentum of the person if the force of friction that keeps a 90-kg person sitting on the edge of a horizontal rotating platform when the person sits 2.1m from the center of the platform and has a tangential speed of 4.0m/s .

F =10 N

Calculate the tension in a horizontal string that whirls a 2.2-kg toy in a circle of radius 2.5m when it moves at 3.4m/s on an icy surface.

τ =10 Nm

Calculate the torque produced by a 52-N perpendicular force at the end of a 0.20-m-long wrench.

rotating

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

the resultant forces and torques must both be zero.

For a system in mechanical equilibrium

near the outside

Horses that move with the fastest linear speed on a merry-go-round are located

double

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

at the center of the Earth.

If the Earth had two identical moons in one circular orbit, and the moons were as far apart in that orbit as they could be, the center of gravity of the Earth-moons system would be

increase

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

the filled jar

Neglecting air resistance, which will roll from rest to the bottom of an incline first, an empty jar, or the same jar filled with peanut butter?

1/3 the distance from the fulcrum

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

two

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

increased mass and increased distance to mass concentration

Rotational inertia about the midpoint of an object becomes greater with _______.

remains the same, but the RPMs decrease

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

62.8 m/min.

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

at its geometrical center

The center of gravity of a basketball is located _______.

at the center of the disk

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

decreases

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

above a place of support

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

wide handle.

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

center of mass

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

External torque

What is required to change the angular momentum of a system?

quadruples the tension in the string

When a rock tied to a string is whirled in a horizontal circle, doubling the speed _______.

doubles

When a rock tied to a string whirled in a horizontal circle somehow doubles in mass but keeps the same speed, the string tension _______.

increases

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

doubles

When the rotational speed of a rotating system doubles, its angular momentum _______.

outside horse

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?

doubles

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

the same and your tangential speed more

A carnival has a Ferris wheel where the seats are located halfway between the center and outside rim. If you were at the outside rim, your angular speed while riding on this Ferris wheel would be

is the disk

A ring and a disk, initially at rest, roll down a hill together. The one to reach the bottom first

sphere

A ring, a disk, and a solid sphere begin rolling down a hill together. The one to reach the bottom first is the

rotation.

A torque acting on an object tends to produce

greater than toward the center

The tangential speed on the outer edge of a rotating carousel is _______.

through its center of gravity

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