Momentum and Collisions — Free Physics Review Games.
This unit covers impulse and momentum, conservation of momentum and collisions — essential concepts for Physics. Use our interactive study games to test your understanding, or review questions in traditional format below.
Pick a mode. Play.
Answer questions as fast as you can. 2 minutes on the clock. Build streaks for bonus points!
Don't want to play?
Review the questions traditionally. Click to expand.
Questions loading...
Focus on understanding.
Focus on understanding core concepts before memorizing details. Use the game modes to test yourself repeatedly — spaced repetition is proven to boost long-term retention.
Related units
This unit covers impulse and momentum, conservation of momentum and collisions — essential concepts for Physics. Use our interactive study games to test your understanding, or review questions in traditional format below.
Key Concepts Breakdown
1 Impulse And Momentum
Momentum is the product of mass and velocity (p = mv) and is a vector quantity. Impulse is the change in momentum, equal to the net force multiplied by the time interval (J = FΔt = Δp). Students must be able to calculate momentum, impulse, and use the impulse-momentum theorem to find unknown forces or time intervals.
Key Points
- p = mv; units are kg·m/s
- Impulse J = FΔt = Δp = mvf − mvi
- Larger Δt for the same Δp means smaller average force (e.g., airbags, padding)
- Momentum is a vector — direction matters when calculating Δp
A 0.5 kg ball moving at 4 m/s to the right is caught and brought to rest in 0.2 s. What is the average force exerted on the ball?
First find Δp: Δp = m(vf − vi) = 0.5(0 − 4) = −2 kg·m/s. Then use J = FΔt: F = Δp / Δt = −2 / 0.2 = −10 N. The negative sign means the force acts to the left, opposing the ball's original motion.
2 Conservation Of Momentum
In a closed system with no net external force, total momentum before an event equals total momentum after (Σp_before = Σp_after). This law applies to all collisions and explosions. Students must be able to set up and solve the conservation equation for unknown velocities.
Key Points
- Σp_before = Σp_after only when net external force = 0
- Applies to both collisions and explosions (objects pushing apart)
- Treat all velocities as signed values — pick a positive direction first
- In an explosion starting from rest, total momentum remains zero
A 2 kg cart moving at 3 m/s east collides with a stationary 1 kg cart. After the collision, the 2 kg cart moves at 1 m/s east. What is the velocity of the 1 kg cart?
Set east as positive. Before: p_total = (2)(3) + (1)(0) = 6 kg·m/s. After: p_total = (2)(1) + (1)(v) = 6. Solving: 2 + v = 6, so v = 4 m/s east. Check by confirming total momentum is conserved: 2 + 4 = 6 ✓.
3 Collisions
Collisions are classified as elastic (kinetic energy conserved), inelastic (KE not fully conserved), or perfectly inelastic (objects stick together, maximum KE lost). Momentum is conserved in all types; kinetic energy is only conserved in elastic collisions. Students must identify collision type and apply the correct equations.
Key Points
- Elastic: both momentum AND kinetic energy are conserved
- Inelastic: momentum conserved, KE is NOT conserved
- Perfectly inelastic: objects stick together; use p_before = (m1 + m2)v_final
- To check if elastic: compare total KE before and after; if equal, it's elastic
A 3 kg object moving at 6 m/s collides and sticks to a stationary 1 kg object. What is their combined velocity after the collision? Is kinetic energy conserved?
Using conservation of momentum: (3)(6) + (1)(0) = (3 + 1)v_f, so 18 = 4v_f, giving v_f = 4.5 m/s. Initial KE = ½(3)(6²) = 54 J; final KE = ½(4)(4.5²) = 40.5 J. Since KE decreased by 13.5 J, this is a perfectly inelastic collision — kinetic energy is not conserved.
Questions, answered.
What is Momentum and Collisions?
Momentum and Collisions is Unit 4 of Physics, covering impulse and momentum, conservation of momentum and collisions.
How to study for Physics Unit 4?
Start with the Quick Summary above, review the Key Concepts, then test yourself with our interactive study games. Aim for 80%+ accuracy before moving on.
How many questions are in this unit?
This unit has 27+ review questions across 5 different game modes.