1.Easy
A 2000 kg car moving at 19 m/s runs into a stationary 1100 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 = 19 m/sm2 = 1100 kgv2 = 0 m/s
v′ = m/s
Momentum & collisions worksheet with answers
2.Easy
A 3.5 kg rifle, free to move, fires a 4 g bullet at 550 m/s. Both start at rest. Find the recoil speed V of the rifle.
M = 3.5 kgm = 4 gv = 550 m/s
V = m/s
3.Medium
A 20 g bullet is fired horizontally into a 4.5 kg wooden block hanging on light strings, and stays inside it. The block swings up until it is 21 cm higher than at the start. Use g = 9.81 m/s². Find the speed v of the bullet before impact.
m = 20 gM = 4.5 kgh = 21 cmg = 9.81 m/s²
v = m/s
4.Medium
A 2000 kg car moving at 6 m/s runs into a stationary 900 kg car and the two lock together. How much kinetic energy ΔK is lost in the collision?
m1 = 2000 kgv1 = 6 m/sm2 = 900 kgv2 = 0
ΔK = J
5.Hard
A 0.25 kg ball hits a wall at 24 m/s and bounces straight back at 10 m/s. The contact lasts 20 ms. Find the magnitude of the impulse J the wall gives the ball.
m = 0.25 kgvin = 24 m/svout = 10 m/sΔt = 20 ms
J = N·s
6.Hard
A 1900 kg car runs into a parked 1100 kg car. The wrecks lock together and skid 14.5 m before stopping. The coefficient of kinetic friction between tyres and road is 0.6. Use g = 9.81 m/s². Find the speed v1 of the first car just before the collision.
m1 = 1900 kgm2 = 1100 kgd = 14.5 mμ = 0.6g = 9.81 m/s²
v1 = m/s
Answer key
- 1. v′ = 12.26 m/s
- 2. V = 0.6286 m/s
- 3. v = 458.7 m/s
- 4. ΔK = 11172 J
- 5. J = 8.5 N·s
- 6. v1 = 20.63 m/s
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