Practice Rotational Equilibrium in Physics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

Rotational equilibrium is the condition in which the net torque on an object is zero, so its angular velocity does not change.

If the clockwise and counterclockwise twists balance, the object will not start spinning faster one way or the other.

Showing a random 20 of 50 problems.

Example 1

medium

Two children,

25\,\text{kg}

1.6\,\text{m}

left and

40\,\text{kg}

on the right of a seesaw pivot, balance (

g = 10\,\text{m/s}^2

). Find the right child's distance.

Example 2

medium

Why is the pivot a useful choice for the torque axis in a static problem?

Example 3

medium

A 6 N weight is

0.3\text{ m}

left of pivot, an 8 N weight is

0.4\text{ m}

right. Find net torque (CCW positive).

Find the net torque (CCW positive).

Example 4

medium

A force of

20\,\text{N}

acts at

30^\circ

to a

0.6\,\text{m}

lever arm. Find the torque about the pivot.

Find the torque about the pivot.

Example 5

easy

A force of

20\text{ N}

acts perpendicular to a wrench

0.25\text{ m}

from the pivot. Find the torque.

Example 6

medium

A uniform

60\text{ N}

horizontal bar,

2\text{ m}

long, is supported by two cables at its ends. Find each cable tension.

Find the tension in each supporting cable.

Example 7

medium

A door is

0.9\text{ m}

wide. A

50\text{ N}

force is applied perpendicular at the handle (far edge). Find the torque about the hinges.

Example 8

challenge

A uniform

80\text{ N}

rod,

1\text{ m}

long, is hinged at one end. A horizontal cable attached at the free end holds it at

30^\circ

above horizontal. Find the cable tension.

Example 9

medium

A meter stick is pivoted at its

50\text{ cm}

mark. A

4\text{ N}

weight sits at

30\text{ cm}

. Find the weight that balances at the

80\text{ cm}

mark.

Find the weight at 80 cm that balances the meter stick.

Example 10

medium

A uniform

30\,\text{N}

bar,

2\,\text{m}

long, is pivoted at one end. Find the torque due to its weight about the pivot.

Find the torque due to the bar's weight about the pivot.

Example 11

easy

A force of

10\,\text{N}

acts perpendicular to a wrench

0.3\,\text{m}

from the pivot. Find the torque.

Example 12

hard

A uniform

200\text{ N}

sign,

2\text{ m}

wide, hangs from two ropes, one at each top corner. A

50\text{ N}

object is attached

0.4\text{ m}

from the left corner. Find the tension in each rope.

Find the tension in each rope.

Example 13

easy

A torque of

15\text{ N·m}

CW and a torque of

7\text{ N·m}

CCW act on a wheel. Find net torque (CCW positive).

Example 14

easy

State the condition for rotational equilibrium about any axis.

Example 15

medium

A uniform

24\,\text{N}

bar,

3\,\text{m}

long, is pivoted at one end. Find the torque due to its weight about the pivot.

Find the torque due to the bar's weight about the pivot.

Example 16

easy

Two equal

15\,\text{N}

weights sit equal distances on opposite sides of a pivot. Is the system in rotational equilibrium?

Example 17

easy

A seesaw has a

20\,\text{N}

weight

1\,\text{m}

left of the pivot and a

10\,\text{N}

weight on the right. For balance, find the right weight's distance.

Example 18

easy

An object is in rotational equilibrium. What is the net torque on it?

Example 19

medium

A 4 N weight is

0.5\,\text{m}

left of a pivot and a 6 N weight is

0.2\,\text{m}

right. Find the net torque (CCW positive).

Find the net torque (CCW positive).

Example 20

medium

A 120 N weight hangs

0.5\text{ m}

from a pivot. A force is applied

1.5\text{ m}

on the other side. Find the force needed for balance.

Find the force needed for equilibrium.

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Related Concepts

Torque Equilibrium