Question

A baseball of mass 250g, pitched with a speed of 40m/s is caught by the catcher, whose glove moves backward 0.25m while stopping the ball. What was the kinetic energy of the ball before it was caught?

Answer 1

The kinetic energy is =.5mv^2 so the amount the glove moved beforehand is irrelevant and typically this is measured in Kgm/s so 250g is .25kg and v^2 is 40x40 so 1600 lastly 1600x.5x.25 is 200kgm/s :)

Answer 2

I don't think we care about the motion of the catcher's glove.

The mass of the ball is 0.25kg and its speed is 40m/s.
So its kinetic energy is . . .

KE = 1/2 (mass) (speed)² =

(0.125 kg) (40m/s)² =

200 kg-m²/s² = 200 joules .