In an ice hockey game a player with red T-shirt hits another player with green T-shirt. After the collision the green T-shirt player who was initially at rest moves with 2 m/s velocity. Masses of red and green T-shirt players are 40kg and 60kg respectively. Find the initial speed of the red T-shirt player?

Explanation:

The collision is elastic as no frictional force exists .

Both momentum and energy will be conserved.

We shall apply velocity formula applicable in respect of elastic collision

m₁ and m₂ be mass of red and green T shirt player , u₁ and u₂ be their initial velocity , v₁ and v₂ be their final velocity

v₂ = (m₂-m₁)u₂ / ( m₁+m₂) + 2 m₁u₁ / ( m₁+m₂)

Given m₁ = 40 kg , m₂ = 60 kg , v₂ = 2 m /s , u₁ = ? , u₂ = 0

Put the values in the equation

2 = 0 + 2 x 40 x u₁ / ( 40 + 60 )

u₁ = 2.5 m /s .

Initial speed of red T- shirt .