Dash is standing on his frictionless skateboard with three balls, each with a mass of 155 g, in his hands. The combined mass of Dash and his skateboard is 65 kg. How fast should dash throw the balls forward if he wants to move backward with a speed of 1.04 m/s?

1.0326 m/s

Explanation:

mass of each ball, m = 155 g = 0.155 kg

mass of Dash and his skateboard, M = 65 kg

Speed of skateboard moving backward, v = 1.04 m/s

Let the speed of the balls in forward direction is u.

By using the conservation of momentum

Momentum in backward direction = Momentum in forward direction

(M + 3m) x u = M x v

(65 + 3 x 0.155) x u = 65 x 1.04

65.465 u = 67.6

u = 1.0326 m/s

Thus, the speed of balls in forward direction is 1.0326 m/s.