A soccer player with a mass of 60 kg is traveling at 8 m/s when he completes a corner kick on a 0.45 kg soccer ball. The soccer ball travels toward the goal at a speed of 35 m/s. In this elastic collision, what is the speed of the soccer player immediately after kicking the ball?

A) 5.4 m/s

B) 7 m/s

C) 7.7 m/s

D) 8 m/s

It must be noted that during an elastic collision both the momentum and kinetic energy are conserved. For the kinetic energy, it can be solved through the equation,

KE = 0.5mv²

Equating the kinetic energies before and after collision,

0.5 (60) (8 m/s) ² = (0.5) (60) (x²) + (0.5) (0.45) (35 m/s) ²

The value of x from the equation is approximately 7.40 m/s