Practice Collisions 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 is an interaction in which objects exert large forces on each other for a short time, changing their momenta.

During a crash or bounce, forces act briefly but strongly, so motion can change a lot.

Showing a random 20 of 50 problems.

Example 1

medium
A 0.05 kg0.05 \text{ kg} bullet at 400 m/s400 \text{ m/s} embeds in a 2 kg2 \text{ kg} block at rest on a frictionless surface. Find the block-bullet speed afterward.

Example 2

medium
A 0.15 kg baseball hits a bat at 40 m/s40\,\text{m/s} and rebounds at 30 m/s30\,\text{m/s}. Find the magnitude of the impulse delivered.

Example 3

hard
A 0.05 kg0.05 \text{ kg} bullet at 300 m/s300 \text{ m/s} passes through a 2 kg2 \text{ kg} block and exits at 100 m/s100 \text{ m/s}. The block sits on a frictionless surface. Find the block's speed afterward.

Example 4

medium
A 1 kg ball at 10 m/s10\,\text{m/s} hits a 1 kg ball at rest; afterward they both move at 5 m/s5\,\text{m/s}. Is this collision elastic?

Example 5

easy
A 0.5 kg ball changes velocity from 00 to 6 m/s6\,\text{m/s} in a collision. Find the impulse on it.

Example 6

medium
Two carts on a frictionless track: m1=2 kgm_1 = 2 \text{ kg} at +3 m/s+3 \text{ m/s}, m2=1 kgm_2 = 1 \text{ kg} at −6 m/s-6 \text{ m/s}. They stick. Find the final velocity.

Example 7

medium
A 1500 kg1500 \text{ kg} car at 20 m/s20 \text{ m/s} collides with a 1000 kg1000 \text{ kg} car at rest; they stick. Find the wreck's speed and the KE lost.

Example 8

hard
A 4 kg4 \text{ kg} object at 6 m/s6 \text{ m/s} collides elastically with a stationary 2 kg2 \text{ kg} object. Find both speeds afterward.

Example 9

medium
A 0.06 kg0.06 \text{ kg} tennis ball is hit by a racket: it comes in at 25 m/s25 \text{ m/s} and leaves at −30 m/s-30 \text{ m/s}. Find the impulse on the ball.

Example 10

easy
A 3 kg object moves at 4 m/s4\,\text{m/s}. Find its momentum.

Example 11

easy
Why do airbags reduce injury in a collision?

Example 12

easy
What single quantity is conserved in every collision (no external forces)?

Example 13

easy
A 2 kg ball at 5 m/s5\,\text{m/s} hits a 2 kg ball at rest. Total momentum before the collision is what?

Example 14

medium
A 0.2 kg0.2 \text{ kg} ball traveling at 10 m/s10 \text{ m/s} strikes a wall and rebounds at −8 m/s-8 \text{ m/s}. Contact lasts 0.05 s0.05 \text{ s}. Find the average force.

Example 15

medium
An astronaut (mass 80 kg80 \text{ kg}) at rest throws a 2 kg2 \text{ kg} wrench at 5 m/s5 \text{ m/s} in space. Find the astronaut's recoil speed.

Example 16

hard
A 1 kg1 \text{ kg} cart moving at 8 m/s8 \text{ m/s} collides perfectly inelastically with a 3 kg3 \text{ kg} cart at rest. Find the fraction of initial KE retained.

Example 17

challenge
A 4 kg block at 3 m/s3\,\text{m/s} collides with a 2 kg block at −3 m/s-3\,\text{m/s}; they stick, then slide onto a rough surface with μk=0.25\mu_k = 0.25 (g=10 m/s2g = 10\,\text{m/s}^2). Find the stopping distance.

Example 18

easy
Impulse on an object equals its change in what?

Example 19

medium
A 3 kg3 \text{ kg} cart at 4 m/s4 \text{ m/s} collides with and sticks to a 5 kg5 \text{ kg} cart at rest. Find their common speed after.

Example 20

medium
A 2 kg2 \text{ kg} ball at 5 m/s5 \text{ m/s} collides head-on elastically with a 2 kg2 \text{ kg} ball at −3 m/s-3 \text{ m/s}. Find both velocities afterward.
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