A0.311 kg tennis racket moving 30.3 m/s east makes an elastic collision with a 0.0570 kg ball moving 19.2 m/s west. find the velocity of the tennis ball after the collision.

15.0 m/s

Explanation:

When elastic collision occurs, the final velocities, v of the bodies are obtained by

Where u and m denote initial velocities and mass while the subscripts 1 and 2 are for tennis ball and the other ball

Substituting 0.311 for mass of tennis, 0.0570 for mass of the other ball, 30.3 m/s for velocity of tennis ball and -19.2 m/s  

here we know that ball will drop down by total distance 3.2 m

so here we know that

now using kinematics

now in the same time it will cover horizontal distance of 0.75 m

so speed of the ball will be