PHSC 1001- Ch. 8 MasteringPhysics

The torque exerted by a crowbar on an object increases with increased _______. A. rotational inertia B. energy of application C. force D. force and leverage distance

D

If a trapeze artist rotates once each second while sailing through the air and contracts to reduce her rotational inertia to one-third of what it was, how many rotations per second will result?

angular momentum is conserved (Li = Lf) L = Iw L = (1/3 * I)(3 w) 3 rotations per second

The rock and meterstick balance at the 25-cm mark, as shown. The meterstick has a mass of 0.50 kg . What must be the mass of the rock?

m = 1.4kg

Calculate the torque produced by a 46-N perpendicular force at the end of a 0.16-m-long wrench. Torque = Lever Arm × Force

τ = 7.4 Nm

The tangential speed on the outer edge of a rotating carousel is _______. A. greater than toward the center B. the same as toward the center C. four times as great for twice the distance D. less than toward the center

A

How is a flywheel constructed to maximize its rotational inertia? A. Most of the mass is concentrated near the axis. B. Most of the mass is concentrated far from the axis. C. Most of the mass is concentrated near a ring half way between the axis and the rim. D. The mass is uniformly distributed across the radius of the disk.

B

What is required to change the angular momentum of a system? A. Force B. External torque C. Torque D. External force

B

You hold a meterstick horizontally with the same mass suspended at the end. Rank the torque needed to keep the stick steady, from largest to smallest.

B, C, A

How does the force needed to turn the wrench change if you increase the lever arm? A. It increases. B. It stays the same. C. It decreases.

C

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

C

How does the lever arm change when you decrease the distance to the nut? A. It increases. B. It stays the same. C. It decreases.

C

The figure below shows two blocks suspended by a single cord over a pulley. (Figure 1) The mass of block B is twice the mass of block A, while the mass of the pulley is equal to the mass of block A. The blocks are let free to move and the cord moves on the pulley without slipping or stretching. There is no friction in the pulley axle, and the cord's weight can be ignored. Which of the following statements correctly describes the system shown in the figure? A. The acceleration of the blocks is zero. B. The net torque on the pulley is zero. C. The angular acceleration of the pulley is nonzero.

C

Distinguish between linear momentum and angular momentum. A. Angular momentum depends on the distribution of mass, whereas linear momentum depends on the total mass. B. Angular momentum depends on the distribution of mass times the total mass, whereas linear momentum depends only on the distribution of mass. C. Angular momentum depends on the total mass, whereas linear momentum depends on the distribution of mass. D. Angular momentum depends on tangential velocity, whereas linear momentum depends on the rotational velocity.

A

The center of gravity of a basketball is located _______. A. in the material making up its mass B. at a point opposite to its center of mass C. at its geometrical center D. at the point of application when balanced

C

What happens when block B moves downward? A. The cord's tension on the left and right side are equal B. The cord's tension on the left side of the pulley is higher than on the right side C. The cord's tension on the right side of the pulley is higher than on the left side

C: Note that if the pulley were stationary (as in many systems where only linear motion is studied), then the tension in the cord on both sides of the pulley would be equal; however, if the pulley rotates with a certain angular acceleration, as in the present situation, the tensions must be different. If they were equal, the pulley could not have an angular acceleration. If the tension of the cord on the left side of the pulley was higher than the tension on the right side, the net torque would make the pulley rotate counterclockwise, and block B would move upward.

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? A. Centripetal force B. It is centripetal force, but only as viewed by someone inside the car. C. There is no force as viewed by someone outside the car. To them you move in a straight line. D. It is centrifugal force as viewed by someone outside the car.

C

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? A. Tangent to the circle in the direction of motion of the can B. Radially outward from the center of the circle C. Toward the center of the circle D. Tangent to the circle and opposite in direction to the motion of the can

C