A trolley has a mass of 1.2 kg and a speed of 4.5 m/s. The trolley crashes into a stationary trolley of mass 0.8 kg. On impact the two trolleys stick together and move off with speed, v. Calculate the momentum of the trolleys before impact. Calculate the speed of the trolleys after impact.

(a) The momentum of the first trolley is 5.4 kgm/s

(b) The velocity of the trolleys after impact is 2.7m/s

Explanation:

Given:

Mass, m₁ = 1.2kg

Velocity, v₁ = 4.5m/s

Mass, m₂ = 0.8kg

v₂ = 0

(a) Momentum of the trolley before impact, p

We know:

Momentum = mass X velocity

p = 1.2 X 4.5

p = 5.4 kgm/s

Therefore, the momentum of the first trolley is 5.4 kgm/s

(b) Speed of the trolleys after impact, v = ?

During collision, the momentum is conserved.

So,

m₁v₁ + m₂v₂ = (m₁ + m₂) v

(1.2 X 4.5) + (0.8 X 0) = (1.2 + 0.8) X v

5.4 + 0 = 2v

v = 2.7m/s

Therefore, the velocity of the trolleys after impact is 2.7m/s