Anthony and Sissy are participating in the "Roll-a-Rama" rollerskating dance championship. While 75.0-kg Anthony roller skates backwards at 3.0 m/s, 60.0-kg Sissy jumps into his arms with a velocity of 5.0 m/s in the same direction. How fast does the pair roll backwards together?

V = 3.89m/s

Explanation:

Given Ma = 75.0kg, Va = 3.0m/s, Ms = 60.0kg and Vs = 5.0m/s

Since the pair roll backwards after Sissy jumps into Anthony's arms,

let the common velocity of the pair be V

From the principle of conservation of momentum,

Total momentum before collision is equal to the total momentum after collision

MaVa + MsVs = (Ma + Ms) * V

V = (MaV + MsVs) / (Ma + Ms)

V = (75*3 + 60*5) / (75 + 60) = 3.89m/s