Chapter 8

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-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 1 kg. 1/2 kg. 1/4 kg. 3/4 kg. none of the above

1 kg

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 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 31.4 m/min. 62.8 m/min. 10 m/min. 100 m/min. need more information

62.8 m/min.

Why can't you stand with your heels and back to a wall and then bend over to touch your toes and return to your stand-up position? Why can't you stand with your heels and back to a wall and then bend over to touch your toes and return to your stand-up position? Your center of gravity does not hang below your support base. Your center of gravity is too high above your support base. A vertical line through the center of gravity of your body is behind your heels, which is outside your support base. A vertical line through the center of gravity of your body is in front of the tips of your toes, which is outside your support base

A vertical line through the center of gravity of your body is in front of the tips of your toes, which is outside your support base

What is the law of inertia for rotating systems in terms of angular momentum? What is the law of inertia for rotating systems in terms of angular momentum? Angular momentum does not change without a change in rotational velocity. Angular momentum does not change without an applied internal torque. Angular momentum does not change without an applied external torque. Angular momentum does not change without a change in rotational inertia.

Angular momentum does not change without an applied external torque.

If a skater who is spinning pulls her arms in so as to reduce her rotational inertia by half, by how much will her angular momentum change? By how much will her rate of spin change? If a skater who is spinning pulls her arms in so as to reduce her rotational inertia by half, by how much will her angular momentum change? By how much will her rate of spin change? Her angular momentum is doubled. Her spin rate is doubled. Her angular momentum does not change. Her spin rate doubles. Her angular momentum is cut in half. Her spin rate is cut in half. Her angular momentum is cut in half. Her spin rate does not change.

Her angular momentum does not change. Her spin rate doubles.

If the string that holds a whirling can in its circular path breaks, what kind of force causes it to move in a straight- line path: centripetal, centrifugal, or no force? What law of physics supports your answer? If the string that holds a whirling can in its circular path breaks, what kind of force causes it to move in a straight- line path: centripetal, centrifugal, or no force? What law of physics supports your answer? Centripetal; Newton's second law. Centrifugal; Newton's first law Centrifugal; Newton's third law No force; Newton's first law

No force; Newton's first law

On a rotating turntable, how do tangential speed and rotational speed vary with distance from the center? On a rotating turntable, how do tangential speed and rotational speed vary with distance from the center? Tangential speed increases with distance. Rotational speed is constant. Rotational speed increases with distance. Tangential speed is constant. Both increase in speed with distance. Both are constant.

Tangential speed increases with distance. Rotational speed is constant.

If you are not wearing a seat belt in a car that rounds a curve, and you slide across your seat and slam against a car door, what kind of force is responsible for your slide: centripetal, centrifugal, or no force? If you are not wearing a seat belt in a car that rounds a curve, and you slide across your seat and slam against a car door, what kind of force is responsible for your slide: centripetal, centrifugal, or no force? It is centrifugal force as viewed by someone outside the car. There is no force as viewed by someone outside the car. To them you move in a straight line. Centripetal force It is centripetal force, but only as viewed by someone inside the car.

There is no force as viewed by someone outside the car. To them you move in a straight line.

What does a torque tend to do to an object? What does a torque tend to do to an object? Torque tends to increase the rotational inertia of the object. Torque tends to increase the linear speed of the object. Torque tends to decrease the rotational inertia of the object. Torque tends to twist or change the state of rotation of the object.

Torque tends to twist or change the state of rotation of the object.

When you whirl a can at the end of a string in a circular path, what is the direction of the force you exert on the can? When you whirl a can at the end of a string in a circular path, what is the direction of the force you exert on the can? Radially outward from the center of the circle Tangent to the circle in the direction of motion of the can Tangent to the circle and opposite in direction to the motion of the can Toward the center of the circle

Toward the center of the circle

Consider someone in a rotating space habitat. Rotational motion provides _______. Consider someone in a rotating space habitat. Rotational motion provides _______. a support force gravity an inertial force a fictitious force

a support force

A vertically-held sledge hammer is easier to balance when the heavier end is A vertically-held sledge hammer is easier to balance when the heavier end is at the top, away from your hand. the same either way on your hand.

at the top, away from your hand.

Centripetal force does no work on a circularly-moving object because Centripetal force does no work on a circularly-moving object because rotational energy transfers to kinetic energy. centripetal force has no component in the direction of motion. no change in energy occurs. none of the above.

centripetal force has no component in the direction of motion.

The net force exerted on a car traveling in a circular path at constant speed is The net force exerted on a car traveling in a circular path at constant speed is zero because the car is not accelerating. directed forward, in the direction of travel. directed toward the center of the curve. none of the above

directed toward the center of the curve.

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 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 remains the same. doubles. halves.

doubles

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 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 twice as fast. at the same linear speed. half as fast.

half as fast

Rotational inertia about the midpoint of an object becomes greater with _______. Rotational inertia about the midpoint of an object becomes greater with _______. decreased mass decreased mass and decreased distance to mass concentration increased mass and increased distance to mass concentration increased mass

increased mass and increased distance to mass concentration

If the rotational speed of a rotating habitat in space increases, the weight experienced by occupants stays the same. decreases. is always zero. increases.

increases

How does the lever arm change if you decrease the angle of the force? How does the lever arm change if you decrease the angle of the force? It stays the same. It increases. It decreases.

it decreases

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 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 shorter. longer. none of these

longer

When a rock tied to a string is whirled in a horizontal circle, doubling the speed _______. When a rock tied to a string is whirled in a horizontal circle, doubling the speed _______. doubles the velocity, but the string tension remains the same quadruples the tension in the string decreases the velocity doubles the tension in the string

quadruples the tension in the string

Centrifugal forces are an apparent reality to observers in a reference frame that is Centrifugal forces are an apparent reality to observers in a reference frame that is moving at constant velocity. an inertial reference frame. rotating. at rest. none of the above

rotating

The rotational inertia of your leg is greater when your leg is The rotational inertia of your leg is greater when your leg is bent. straight. same either way

straight

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? 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? 1 and 1/2 times 1/2 4 times twice the same

the same

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.) 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.) with ice both the same with water need more information

with water