Practice Inelastic Collision in Physics

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

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Quick Recap

A collision in which the total momentum of the system is conserved but the total kinetic energy is not — some kinetic energy is converted.

Two cars crashing and sticking together: they move as one object and kinetic energy is lost.

Showing a random 20 of 50 problems.

Example 1

hard
Ballistic pendulum: a 0.01 kg0.01 \text{ kg} bullet embeds in a 0.99 kg0.99 \text{ kg} pendulum at rest. The combined block rises 0.45 m0.45 \text{ m} (g=10 m/s2g = 10 \text{ m/s}^2). Find the bullet's initial speed.

Example 2

medium
A 2 kg cart at 6 m/s6\,\text{m/s} sticks to a 4 kg cart at rest. Find the common velocity.

Example 3

medium
A 1 kg1 \text{ kg} ball at 10 m/s10 \text{ m/s} hits a 3 kg3 \text{ kg} ball at rest; they stick. Find vfv_f and the fraction of KE retained.

Example 4

easy
Total momentum before a perfectly inelastic collision is 20 kg\cdotpm/s20\,\text{kg·m/s} and the combined mass is 5 kg5\,\text{kg}. Find the final speed.

Example 5

easy
Energy lost in an inelastic collision goes mainly to what forms?

Example 6

hard
A 4 kg4 \text{ kg} block at 6 m/s6 \text{ m/s} sticks to a 2 kg2 \text{ kg} block at rest; the combined mass slides onto a μk=0.5\mu_k = 0.5 patch (g=10 m/s2g = 10 \text{ m/s}^2). How far does it slide?

Example 7

challenge
A 3 kg cart at 4 m/s4\,\text{m/s} collides and sticks with a 1 kg cart moving toward it at 4 m/s4\,\text{m/s}. Find the final velocity and the percentage of kinetic energy lost.

Example 8

medium
A 0.05 kg bullet at 400 m/s400\,\text{m/s} embeds in a 1.95 kg block at rest. Find the speed of the block-plus-bullet.

Example 9

medium
A perfectly inelastic collision happens between equal masses, one at rest. What fraction of the initial KE is lost?

Example 10

medium
Two clay balls, 2 kg at 6 m/s6\,\text{m/s} and 3 kg at −1 m/s-1\,\text{m/s}, collide and stick. Find the final velocity.

Example 11

medium
A 2 kg block slides at 9 m/s9\,\text{m/s} and catches a 1 kg block at 3 m/s3\,\text{m/s} (same direction); they stick. Find the final velocity.

Example 12

medium
Why is momentum conserved in an inelastic collision even though kinetic energy is not?

Example 13

medium
A 6 kg6 \text{ kg} object initially moving at 5 m/s5 \text{ m/s} collides with and sticks to a stationary object; the combined system ends at 3 m/s3 \text{ m/s}. Find the unknown mass.

Example 14

medium
2 kg2 \text{ kg} at 4 m/s4 \text{ m/s} hits and sticks to 3 kg3 \text{ kg} moving the same direction at 1 m/s1 \text{ m/s}. Find vfv_f.

Example 15

medium
A 5 kg object at 4 m/s4\,\text{m/s} collides and sticks with an object, ending at 2 m/s2\,\text{m/s}. Find the mass of the second object (initially at rest).

Example 16

challenge
A 0.02 kg0.02 \text{ kg} bullet at 400 m/s400 \text{ m/s} embeds in a 4 kg4 \text{ kg} wooden block hanging on a string (g=10 m/s2g = 10 \text{ m/s}^2). Find the maximum angle through which the block swings if the string is 1 m1 \text{ m} long.

Example 17

easy
A 0.4 kg0.4 \text{ kg} glob of clay at 5 m/s5 \text{ m/s} hits and sticks to a 0.1 kg0.1 \text{ kg} glob at rest. Find vfv_f.

Example 18

easy
Which quantity is conserved in an inelastic collision: momentum, kinetic energy, or both?

Example 19

easy
Two 2 kg2 \text{ kg} lumps move at +3 m/s+3 \text{ m/s} and −1 m/s-1 \text{ m/s} and stick. Find vfv_f.

Example 20

medium
A 0.1 kg ball of clay at 12 m/s12\,\text{m/s} sticks to a 0.3 kg ball at rest. Find the common speed.
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