A52 g plastic ball is moving to the left at 24 m/s . how much work must be done on the ball to cause it to move to the right at 24 m/s ?

For the work-energy theorem, the work done must be equal to the variation of kinetic energy of the ball:

where is the mass of the ball, and where is the variation of velocity of the ball.
The initial velocity of the ball is +24 m/s, while the final velocity is -24 m/s (the negative sign is due to the fact the ball goes now in the opposite direction), so the variation of velocity is

Therefore, substituting all the numbers in the formula we find the work done: