Practice Equilibrium in Physics

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

Worksheet PDF Free Answer-key PDF Family

Quick Recap

A state in which all forces acting on an object balance so that the net force equals zero and there is no acceleration.

All forces cancel out — the object doesn't accelerate, though it may still be moving at constant velocity.

Showing a random 20 of 50 problems.

Example 1

medium
A box is pushed right at 1212 N and stays still due to friction. What is the friction force?

Example 2

hard
For 2A⇌B2\text{A} \rightleftharpoons \text{B} with K1K_1, what is K for 4A⇌2B4\text{A} \rightleftharpoons 2\text{B}?

Example 3

medium
A 22 kg block rests on a 30∘30^\circ frictionless incline against a horizontal wall at its base. Is it in equilibrium without friction? Explain with the slope-direction net force.

Example 4

easy
For A+B⇌C\text{A}+\text{B} \rightleftharpoons \text{C}, write the equilibrium expression KK.

Example 5

medium
For H2+I2⇌2HI\text{H}_2 + \text{I}_2 \rightleftharpoons 2\text{HI}, at equilibrium [H2]=0.20 M[\text{H}_2] = 0.20\,\text{M}, [I2]=0.20 M[\text{I}_2] = 0.20\,\text{M}, [HI]=1.00 M[\text{HI}] = 1.00\,\text{M}. Find KK.

Example 6

easy
Which arrow symbol indicates a reversible reaction at equilibrium?

Example 7

medium
A 55 kg sign hangs from a single rope. A side wind pushes it horizontally with 3030 N, holding the rope at an angle. Find the rope tension (g=10g=10 m/s2^2).

Example 8

easy
Is a system at chemical equilibrium static or dynamic?

Example 9

easy
Does "at equilibrium" mean the concentrations of reactants and products are necessarily equal?

Example 10

medium
For N2O4⇌2NO2\text{N}_2\text{O}_4 \rightleftharpoons 2\text{NO}_2, K=0.211K = 0.211 at equilibrium [N2O4]=0.500 M[\text{N}_2\text{O}_4] = 0.500\,\text{M}. Find [NO2][\text{NO}_2].

Example 11

medium
Given A⇌B\text{A} \rightleftharpoons \text{B} with K=3.0K = 3.0. At equilibrium [A]=0.20 M[\text{A}] = 0.20\,\text{M}. Find [B][\text{B}].

Example 12

easy
Three horizontal forces give equilibrium. Two are 55 N left and 33 N left. What is the third?

Example 13

challenge
A 44 kg mass hangs from ropes A (horizontal) and B (at 30∘30^\circ above horizontal from a wall). Find tension in rope B (g=10g=10 m/s2^2).

Example 14

easy
A crate slides at a constant 33 m/s across a floor. Is it in equilibrium?

Example 15

easy
A 55 kg lamp hangs at rest from a cord (g=10g=10 m/s2^2). What is the cord's tension?

Example 16

medium
A 1010 kg traffic light hangs from two cables at 45∘45^\circ each from the horizontal (g=10g=10 m/s2^2). Find each tension.

Example 17

medium
A 66 kg block on a 30∘30^\circ incline is held at rest by a rope along the slope (g=10g=10 m/s2^2, frictionless). Find the tension.

Example 18

medium
An object is in equilibrium under three forces: F1=10 NF_1 = 10 \text{ N} east, F2=10 NF_2 = 10 \text{ N} north. What is the magnitude and direction of the third force F3F_3?

Example 19

challenge
For H2+I2⇌2HI\text{H}_2 + \text{I}_2 \rightleftharpoons 2\text{HI}, K=50K = 50. If [H2]0=[I2]0=1.00 M[\text{H}_2]_0 = [\text{I}_2]_0 = 1.00\,\text{M}, no HI initially, find [HI][\text{HI}] at equilibrium.

Example 20

challenge
A uniform 66 m, 2020 N beam is supported at both ends. A 6060 N weight sits 22 m from the left end. Find the left support force.
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