Question

two spheres approach each other and collide elastically. If the masses are equal and the speeds are v1=3.0m/s and v2=-5.0m/s. Determine the final speeds of each

Answer 1

given

masses are equal

m₁ = m₂ = m

v₁ = 3.0 m/sec

and

v₂ = - 5.0 m/sec

the final speed is v_f = ?

using the conservation of momentum

because the two spheres approach each other and collide elastically

m₁ v₁ + m₂ v₂ = ( m₁ + m₂ ) v_f

m x 3 - m x 5 = ( m + m ) x v_f

m ( 3 - 5 ) = 2 m x v_f

- 2 = 2 x v_f

v_f = - 1 m/sec

so the final speeds of each sphere is v_f = - 1 m/sec

here negative sign shows the direction.