What is the new speed

Question

A 7-kg bowling ball rolls at 9 m/s towards the stationary pins. The bowling ball hits the 2-kg pin, launching it forward at 14 m/s. What is the new speed of the bowling ball

Answer 1

Use conservation of linear momentum.

 

Mv₁ = Mv₂ + mu

 

M = 7 kg

v₁ = 9 m/s

m = 2 kg

u = 14 m/s

v₂ = ?

 

v₂ = (Mv₁ - mu)/M = [7(9)- 2(14)]/7 m/s = 5 m/s

 

v₂ is in the same direction as v₁