Q: Which of the following is true for a rigid body in true equilibrium?

$$F_{\mathrm{net}} = 0$$ and $$\tau_{\mathrm{net}} = 0$$

Q: A 12.0 cm diameter disc spins at 5.0 rpm. What is the tangential speed at a point 3.0 cm from the center?

$$1.6 \times 10$$^{-2}$$\ \mathrm{m/s}$$

Question 1

A disc with a diameter of 12.0 cm spins at 5.0 rpm about its center. What is its angular speed in SI units (radians per second)?

Accepted Answer

$$0.52\ \mathrm{rad/s}$$

Question 2

A force $$F is $$applied at a distance $$r$$ from the axis of rotation, making an angle $$\phi$$ with the radial line. Which equation correctly gives the magnitude of the torque produced?

Accepted Answer

$$	au = rF\sin\phi$$

Question 3

A force is applied tangentially at a point 0.10 m from the axis of a wheel, producing a torque of $$0.5\ \mathrm{N\cdot m}. $$What is the magnitude of the applied force?

Accepted Answer

$$5.0\ \mathrm{N}$$

Question 4

Which of the following statements about torque is correct?

Accepted Answer

Torque can only change rotational motion and acts tangentially to the radius.

Question 5

A force is applied at the center of mass of a freely moveable object. What is the resulting motion?

Accepted Answer

The object accelerates translationally without rotating.

Question 6

A force of $$10\ \mathrm{N} is $$applied at a distance of $$0.2\ \mathrm{m}$$ from the axis of rotation at an angle of $$30^\circ to $$the radius. What is the torque produced?

Accepted Answer

$$1.0\ \mathrm{N\cdot m}$$

Question 7

Which of the following is true for a rigid body in true equilibrium?

Accepted Answer

$$F_{\mathrm{net}} = 0$$ and $$	au_{\mathrm{net}} = 0$$

Question 8

A force is applied parallel to the radius of a rotating object at a distance $$r$$ from the axis. What is the torque produced?

Accepted Answer

$$0$$

Question 9

A 12.0 cm diameter disc spins at 5.0 rpm. What is the tangential speed at a point 3.0 cm from the center?

Accepted Answer

$$1.6 	imes 10$$^{-2}$$\ \mathrm{m/s}$$

Question 10

Which of the following best describes the effect of increasing the distance from the axis of rotation when applying the same force?

Accepted Answer

The torque increases.

Question 11

A force of $$8\ \mathrm{N} is $$applied perpendicular to a lever arm $$0.5\ \mathrm{m}$$ from the pivot. What is the resulting torque?

Accepted Answer

$$4.0\ \mathrm{N\cdot m}$$

Question 12

Which of the following is NOT a requirement for true equilibrium of a rigid body?

Accepted Answer

The net force must be nonzero.

Question 13

A force is applied at a point on a rigid body, not at the center of mass. What is the most likely result?

Accepted Answer

The object will rotate about the axis of rotation.

Question 14

Which of the following best describes the right-hand curl rule for torque direction?

Accepted Answer

Curl your fingers in the direction of rotation; your thumb points in the direction of the torque vector.

Question 15

A spot is found 3.0 cm from the center of a spinning disc. How many radians does it travel in 7.0 s if the disc spins at 5.0 rpm?

Accepted Answer

$$3.7$$

Question 16

Which of the following is a correct comparison between torque and force?

Accepted Answer

Torque can only change rotation, while force can change both rotation and translation.

Question 17

A force is applied at the axis of rotation of a rigid body. What torque does it produce?

Accepted Answer

$$0$$

Question 18

Which of the following is a synonym pair according to the study materials?

Accepted Answer

Rotational and Angular

Question 19

If the net force on a system is zero but the net torque is not zero, what will happen?

Accepted Answer

The system will rotate but not translate.

Question 20

Which of the following best explains why gravitational force acting at the axis of rotation produces no torque?

Accepted Answer

Because the radial displacement $$r = 0 at $$the axis.

Rotational Motion and Torque: Angular Kinematics, Forces, and Equilibrium

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