Q: A wrench is used to tighten a nut. The handle is tilted $$30^ ext{o}$$ above the horizontal, and a force of 100 N is exerted straight down at a distance of 0.2 m from the nut. What is the torque about the nut?

$$\tau = 0.2 \times 100 \times \sin(60^ ext{o}) = 17.3\ \text{N} \cdot \text{m}$$

Q: A seesaw is balanced when a 150 lb man sits at a distance $$r$$ from the center to balance a 40 lb child sitting at the other end, 6 ft from the center. What is the value of $$r$$?

$$r = \frac{6 \times 40}{150} = 1.6\ \text{ft}$$

Q: A force of 50 N is applied perpendicular to a lever 0.5 m from the pivot. What is the torque?

$$\tau = 50 \times 0.5 \times \sin(90^ ext{o}) = 25\ \text{N} \cdot \text{m}$$

Q: If a force is applied at an angle $$\theta to $$the lever arm, which component of the force contributes to the torque?

The perpendicular component: $$F_{\perp} = F \sin \theta$$

Question 1

Which of the following best describes torque?

Accepted Answer

The rotational equivalent of force

Question 2

A student pushes on a door 0.7 m from the hinge with a force of 240 N at an angle of $$20^	ext{o}$$ from the line of the door. What is the magnitude of the torque produced?

Accepted Answer

Question 3

Which of the following factors does NOT affect the magnitude of torque produced by a force?

Accepted Answer

The mass of the object being rotated

Question 4

What is the correct formula for torque when a force $$F is $$applied at a distance $$r$$ from the axis at an angle $$	heta$$?

Accepted Answer

$$	au = rF\sin	heta$$

Question 5

A wrench is used to tighten a nut. The handle is tilted $$30^	ext{o}$$ above the horizontal, and a force of 100 N is exerted straight down at a distance of 0.2 m from the nut. What is the torque about the nut?

Accepted Answer

$$	au = 0.2 	imes 100 	imes \sin(60^	ext{o}) = 17.3\ 	ext{N} \cdot 	ext{m}$$

Question 6

If multiple forces act on a body about a pivot, how is the net torque calculated?

Accepted Answer

By summing the torques due to each force, considering their direction: $$	au_{	ext{net}} = \sum 	au$$

Question 7

A seesaw is balanced when a 150 lb man sits at a distance $$r$$ from the center to balance a 40 lb child sitting at the other end, 6 ft from the center. What is the value of $$r$$?

Accepted Answer

$$r = \frac{6 	imes 40}{150} = 1.6\ 	ext{ft}$$

Question 8

Which of the following statements about torque is TRUE?

Accepted Answer

Torque is zero when the force is applied at the pivot point

Question 9

A force of 50 N is applied perpendicular to a lever 0.5 m from the pivot. What is the torque?

Accepted Answer

$$	au = 50 	imes 0.5 	imes \sin(90^	ext{o}) = 25\ 	ext{N} \cdot 	ext{m}$$

Question 10

Which unit is used to measure torque?

Accepted Answer

Newton-meter (N·m)

Question 11

If a force is applied at an angle $$	heta to $$the lever arm, which component of the force contributes to the torque?

Accepted Answer

The perpendicular component: $$F_{\perp} = F \sin 	heta$$

Question 12

A door is stuck and a student pushes at a point 0.7 m from the hinge with a force of 240 N directed $$20^	ext{o}$$ from the line to the door. What is the correct angle to use in the torque calculation?

Accepted Answer

$$70^	ext{o}$$

Question 13

Which scenario will produce the greatest torque?

Accepted Answer

Applying a large force far from the pivot and perpendicular to the lever arm

Question 14

If the net torque on a system is zero, what can be said about the system?

Accepted Answer

It is in rotational equilibrium

Question 15

A force $$F is $$applied at a distance $$r$$ from the axis at an angle $$	heta. $$Which equation gives the perpendicular component of the force?

Accepted Answer

$$F_{\perp} = F \sin 	heta$$

Question 16

A solid rod is pivoted at one end. Which of the following will result in zero torque?

Accepted Answer

Applying a force parallel to the rod at the free end

Question 17

If a force is applied at a distance $$r$$ from the axis, but along the line connecting the axis and the point of application, what is the torque?

Accepted Answer

$$	au = rF\sin(0) = 0$$

Question 18

Which of the following best explains why a longer wrench makes it easier to loosen a tight bolt?

Accepted Answer

A longer wrench increases the distance $$r$$, thus increasing the torque for the same force

Question 19

A force of 80 N is applied at a distance of 0.5 m from the axis at an angle of $$45^	ext{o}. $$What is the torque?

Accepted Answer

$$	au = 0.5 	imes 80 	imes \sin(45^	ext{o}) = 28.3\ 	ext{N} \cdot 	ext{m}$$

Torque and Rotational Equilibrium: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards