Calculating Work Done by a Pitcher: Physics Homework [SOLVED]

[Heat]

[SOLVED] Work Done by Pitcher

Homework Statement

A baseball leaves a pitcher's hand at a speed of 32.5 m/s. The mass of the baseball is 0.145 kg. You can ignore air resistance.

How much work has the pitcher done on the ball by throwing it?

The Attempt at a Solution

velocity initial = 32.5
velocity final = 0 (it has to stop eventually right?)
mass of ball = .145

K = mv^2

K1 = (.145)(32.5)^2 = 153.16
K2 = (.145)(0)^2 = 0

Wtotal = K2-K1

Wtotal = 0 - 153.16



Solution: 76.6 J

 

[Doc Al]

How much work has the pitcher done on the ball by throwing it?

They are talking about the work done by the pitcher in taking a ball from rest to its top speed as it leaves his hand.

K = mv^2

That's not quite right.

 

[Heat]

haha,

I forgot it was

K = 1/2mv^2

ok, now that I got 76.58.

ah, I see now.

so it's this then

K2 = .5(.145)(32.5)^2 = 153.16
K1 = .5(.145)(0)^2 = 0

Wtot = K2-K1 = 76.58