Question 1

A disk and a hoop, each with the same mass and radius, are released from rest at the top of an incline. Which one reaches the bottom first, and why?

Accepted Answer

The disk, because it has less rotational inertia.

Question 2

Which of the following best describes the relationship between tangential speed $$v$$, rotational speed $$\omega$$, and radius $$r$$ for a point on a rotating object?

Accepted Answer

$$v = r \omega$$

Question 3

A tightrope walker uses a long pole to help maintain balance. What physical principle explains why the pole helps?

Accepted Answer

The pole increases the walker's rotational inertia.

Question 4

A wrench is used to loosen a bolt. Which of the following actions will increase the torque applied to the bolt?

Accepted Answer

Applying the force perpendicular to the wrench at its end.

Question 5

A car rounds a curve of radius $$r at $$speed $$v. If $$the speed is doubled, by what factor must the centripetal force increase to keep the car on the road?

Accepted Answer

It must increase by a factor of four.

Question 6

Which of the following statements about centrifugal force is correct?

Accepted Answer

It is an apparent force observed in a rotating reference frame.

Question 7

A space station is designed to simulate gravity by rotating. If the radius of the station is doubled, what must happen to the rotational speed to maintain the same simulated gravity?

Accepted Answer

It must be reduced by a factor of $$\sqrt{2}.$$

Question 8

A figure skater pulls in her arms during a spin. What happens to her rotational speed and why?

Accepted Answer

Her rotational speed increases because her rotational inertia decreases.

Question 9

Which of the following best describes the law of conservation of angular momentum?

Accepted Answer

If no external net torque acts on a system, its angular momentum remains constant.

Question 10

A child sits on a merry-go-round halfway between the center and the edge, moving at a tangential speed of $$2\ \mathrm{m/s}. $$What is the tangential speed of another child sitting at the edge?

Accepted Answer

$$4\ \mathrm{m/s}$$

Question 11

A uniform stick is rotated about one end and then about its center of gravity. Which configuration has greater rotational inertia?

Accepted Answer

Rotating about the end.

Question 12

A 200 N girl sits 3 m from the pivot of a seesaw. If she is handed a 40 N bag of apples, how far from the pivot should her seat be hung to maintain balance?

Accepted Answer

2.5 m

Question 13

Which of the following is true about the center of gravity of an object?

Accepted Answer

It is the average position of the weight distribution.

Question 14

A ball is whirled in a horizontal circle at the end of a string. If the string breaks, what path does the ball follow?

Accepted Answer

It moves in a straight line tangent to the circle.

Question 15

Suppose you are swirling a can around and suddenly pull the rope in halfway. By what factor does the speed of the can change, assuming no external torque acts?

Accepted Answer

It doubles.

Question 16

A car enters a sharper curve with half the radius of curvature but at the same speed. By what factor must the centripetal force change to prevent skidding?

Accepted Answer

It must double.

Question 17

Which of the following is NOT a factor that affects the torque produced by a force?

Accepted Answer

The mass of the object.

Question 18

A solid sphere and a solid cylinder, both with the same mass and radius, are rolled down an incline. Which one reaches the bottom first and why?

Accepted Answer

The solid sphere, because it has less rotational inertia.

Question 19

If the rotational inertia of a spinning figure skater is reduced to half by pulling in her arms, by what factor does her angular velocity change (assuming angular momentum is conserved)?

Accepted Answer

It doubles.

Rotational Motion: Physics with Calculus Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards