Question

A block of mass 1 kg traveling in a straight line with a velocity of 10 ms^–1 collides with and sticks to a stationary wooden block of mass 5 kg.
Then they both move off together in the same straight line. Calculate the total momentum just before the impact, just after the impact and the velocity of the combined object.

• A. 10 kg ms^-1, 20 kgms^-1, 1.67 ms^-1
• B. 10 kg ms^-1, 10 kg ms^-1, 2 ms^-1
• C. 10 kg ms^-1, 10 kg ms^-1, 1.67 ms^-1
• D. 5 kg ms^-1, 10 kg ms^-1, 2 ms^-1

Answer 1

The correct option is C

10 kg ms^-1, 10 kg ms^-1, 1.67 ms^-1

Given, m₁ =1 kg, u₁ = 10 m/s and m₂ = 5 kg, u₂ = 0

The momentum before collision = m₁u₁+m₂u₂ = 10 kgm/s.

The momentum after collision = (m₁+m₂) x v = 6 v.

From the law of conservation of momentum, momentum before collision should be equal to momentum after the collision as no external force was acting on the bodies. So,

6 v = 10

v = 1.67 m/s