1.Easy
A 4 kg rifle, free to move, fires an 8 g bullet at 450 m/s. Both start at rest. Find the recoil speed V of the rifle.
M = 4 kgm = 8 gv = 450 m/s
V = m/s
Momentum & collisions worksheet with answers
2.Easy
A 4 kg trolley moving at 3.5 m/s runs into a 3 kg trolley at rest. After the collision the first trolley continues in the same direction at 1 m/s. Find the velocity v′2 of the second trolley.
m1 = 4 kgv1 = 3.5 m/sm2 = 3 kgv′1 = 1 m/s
v′2 = m/s
3.Medium
A 5 g bullet is fired horizontally into a 2.5 kg wooden block hanging on light strings, and stays inside it. The block swings up until it is 6 cm higher than at the start. Use g = 9.81 m/s². Find the speed v of the bullet before impact.
m = 5 gM = 2.5 kgh = 6 cmg = 9.81 m/s²
v = m/s
4.Medium
A 1.5 kg glider moving at 2 m/s makes a perfectly elastic head-on collision with a 4 kg glider at rest on a frictionless track. Find the velocity v′2 of the second glider after the collision.
m1 = 1.5 kgm2 = 4 kgv1 = 2 m/sv2 = 0
v′2 = m/s
5.Hard
A 1500 kg car runs into a parked 1800 kg car. The wrecks lock together and skid 9 m before stopping. The coefficient of kinetic friction between tyres and road is 0.5. Use g = 9.81 m/s². Find the speed v1 of the first car just before the collision.
m1 = 1500 kgm2 = 1800 kgd = 9 mμ = 0.5g = 9.81 m/s²
v1 = m/s
6.Hard
At a crossing an 800 kg car travelling east at 22 m/s collides with a 900 kg car travelling north at 8 m/s. The cars lock together. Find the speed v′ of the wreck just after the collision.
m1 = 800 kgv1 = 22 m/s (E)m2 = 900 kgv2 = 8 m/s (N)
v′ = m/s
Answer key
- 1. V = 0.9 m/s
- 2. v′2 = 3.333 m/s
- 3. v = 543.6 m/s
- 4. v′2 = 1.091 m/s
- 5. v1 = 20.67 m/s
- 6. v′ = 11.19 m/s
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