Question

A hockey ball of mass .5 Kg travelling at 10 ms-1 is struck by a hockey stick so as to return it along its original path with a velocity at 5m/s. Calculate the change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick.

Answer 1

Given :

• mass of hockey ball, m = 0.5 kg
• initial velocity of ball (velocity before collision to hockey stick) , u = 10 ms⁻¹
• final velocity of ball (velocity after collision to hockey stick) , v = 5 ms⁻¹

To find :

• change in momentum in motion of hockey ball , Δ p = ?

Formulae required :

Formula to calculate momentum

• p = m v

[ where p is momentum , m is mass and v is velocity of body ]

Change in momentum is given by

• Δp = m v - m u

[ where Δ p is change is momentum, m is mass of body, u is initial velocity of body, v is final velocity of body ]

Calculation :

Calculating initial momentum of ball ( p₁ )

→ p₁ = m u

→ p₁ = (0.5) × (10)

→ p₁ = 5  kg ms⁻¹

Calculating final momentum of ball ( p₂ )

→ p₂ = m v

→ p₂ = (0.5) × (5)

→ p₂ = 2.5 kg ms⁻¹

Calculating change in momentum (Δ p )

→ Δ p = p₂ - p₁

→ Δ p = m v - m u

→ Δ p = 2.5 - 5

→ Δ p = -2.5 kg ms⁻¹

therefore,

Change in momentum of ball is -2.5 kg ms⁻¹.

( negative sign shows that Ball after collision will move in opposite direction )