Practice Conservation of Momentum in Physics

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

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Quick Recap

In a closed system with no net external force, the total momentum of all objects remains constant before and after any interaction — momentum is conserved.

Momentum can move between objects but can't be created or destroyed.

Showing a random 20 of 50 problems.

Example 1

medium

0.5\text{ kg}

ball moving east at

3\text{ m/s}

collides with a

0.5\text{ kg}

ball moving north at

4\text{ m/s}

and they stick. Find the speed of the combined object.

Example 2

medium

5 \text{ kg}

cart moving at

4 \text{ m/s}

collides with a stationary

3 \text{ kg}

cart. They stick together. What is their final velocity?

Example 3

challenge

5\text{ kg}

object at rest explodes into three equal

\tfrac{5}{3}\text{ kg}

fragments. Two fly off perpendicularly at

6\text{ m/s}

each. Find the speed and direction of the third fragment.

Example 4

medium

2

kg ball at

3

m/s east strikes a

2

kg ball at

4

m/s north; they stick. Find the speed of the combined object.

Example 5

easy

A stationary

5

kg object explodes into two pieces. One piece carries

+12

\cdot

m/s. What is the other piece's momentum?

Example 6

hard

1500\text{ kg}

rocket ejects

0.5\text{ kg}

of gas per second at

1000\text{ m/s}

relative to the rocket. Find the thrust force.

Example 7

challenge

A ballistic pendulum: a

0.02

kg bullet embeds in a

1.98

kg block, which then rises

0.2

m (

g=10

m/s

^2

). Find the bullet's initial speed.

Example 8

medium

0.05

kg bullet at

400

m/s embeds in a

2.95

kg block at rest. Find the block-bullet speed after.

Example 9

easy

70\text{ kg}

person on frictionless ice throws a

5\text{ kg}

ball at

4\text{ m/s}

east. Find the person's velocity.

Example 10

easy

0.04\text{ kg}

bullet at

300\text{ m/s}

embeds in a

4\text{ kg}

block at rest. Find their joint speed.

Example 11

hard

0.05\text{ kg}

bullet is fired horizontally from a

4\text{ kg}

rifle, leaving at

400\text{ m/s}

relative to the ground. Find the rifle's recoil speed.

Example 12

medium

0.15\text{ kg}

baseball at

40\text{ m/s}

is hit and rebounds at

50\text{ m/s}

in the opposite direction. Find the magnitude of the impulse on the ball.

Example 13

medium

2\text{ kg}

ball at

4\text{ m/s}

collides elastically with a

2\text{ kg}

ball at rest. Find their final velocities.

Example 14

hard

Two ice skaters push off from rest. Skater A (

45\text{ kg}

) drifts east at

2\text{ m/s}

. Skater B (

60\text{ kg}

) drifts ___?

Example 15

easy

1\text{ kg}

object at

5\text{ m/s}

collides with a

1\text{ kg}

object at

-3\text{ m/s}

and they stick. Find their final velocity.

Example 16

easy

3

kg ball at

4

m/s hits a

3

kg ball at rest and stops dead. What is the second ball's velocity?

Example 17

easy

10

kg cart at

6

m/s couples with a

20

kg cart at rest. Find their joint speed.

Example 18

medium

2

kg object at

5

m/s collides with a

3

kg object at

-2

m/s and they stick. Find the final velocity.

Example 19

easy

3\text{ kg}

cart at

4\text{ m/s}

collides with a

5\text{ kg}

cart at rest. They stick. Find their common speed.

Example 20

medium

4\text{ kg}

object at rest explodes into a

1\text{ kg}

piece going

+8\text{ m/s}

and a

3\text{ kg}

piece. Find the

3\text{ kg}

piece's velocity.

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Related Concepts

Momentum Impulse Elastic Collision Inelastic Collision