1.Easy
A 4.5 kg rifle, free to move, fires a 4 g bullet at 650 m/s. Both start at rest. Find the recoil speed V of the rifle.
M = 4.5 kgm = 4 gv = 650 m/s
V = m/s
Momentum & collisions worksheet with answers
2.Easy
A 2000 kg car moving at 9 m/s runs into a stationary 1600 kg car. The cars lock together. Find their common velocity v′ just after the collision (positive in the first car’s direction).
m1 = 2000 kgv1 = 9 m/sm2 = 1600 kgv2 = 0 m/s
v′ = m/s
3.Medium
A 12 kg projectile moving horizontally at 24 m/s explodes into two fragments that move along the same line. The 7 kg fragment continues forwards at 81 m/s. Find the velocity v′2 of the 5 kg fragment (positive in the original direction).
M = 12 kgu = 24 m/sm1 = 7 kgv′1 = 81 m/sm2 = 5 kg
v′2 = m/s
4.Medium
A 3.5 kg glider moving at 8 m/s makes a perfectly elastic head-on collision with a 5 kg glider at rest on a frictionless track. Find the velocity v′2 of the second glider after the collision.
m1 = 3.5 kgm2 = 5 kgv1 = 8 m/sv2 = 0
v′2 = m/s
5.Hard
A 0.1 kg ball hits a wall at 10 m/s and bounces straight back at 18 m/s. The contact lasts 5 ms. Find the average force Favg of the wall on the ball.
m = 0.1 kgvin = 10 m/svout = 18 m/sΔt = 5 ms
Favg = N
6.Hard
A 1300 kg car runs into a parked 1000 kg car. The wrecks lock together and skid 19.5 m before stopping. The coefficient of kinetic friction between tyres and road is 0.7. Use g = 9.81 m/s². Find the speed v1 of the first car just before the collision.
m1 = 1300 kgm2 = 1000 kgd = 19.5 mμ = 0.7g = 9.81 m/s²
v1 = m/s
Answer key
- 1. V = 0.5778 m/s
- 2. v′ = 5 m/s
- 3. v′2 = −55.8 m/s
- 4. v′2 = 6.588 m/s
- 5. Favg = 560 N
- 6. v1 = 28.95 m/s
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