# Work / kinetic energy

• August 25th 2007, 02:47 AM
Work / kinetic energy
A baseball pitcher throws a fastball that leaves his hand at a speed of 36.0m/s. The mass of the baseball is 0.145kg. Ignore air resistance. How much work has the pitcher done on the ball in throwing it?

I dunno what to use

$W = \frac{1}{2}m{v_{2}}^2 - \frac{1}{2}m{v_{1}}^2$

• August 25th 2007, 03:23 AM
CaptainBlack
Quote:

A baseball pitcher throws a fastball that leaves his hand at a speed of 36.0m/s. The mass of the baseball is 0.145kg. Ignore air resistance. How much work has the pitcher done on the ball in throwing it?

I dunno what to use

$W = \frac{1}{2}m{v_{2}}^2 - \frac{1}{2}m{v_{1}}^2$

The work done is equal to the change in KE of the ball. In this case the initial
KE is zero (zero speed), and the final KE is $\frac{0.145\times 36^2}{2}$

RonL