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## Homework Statement

An outfielder throws a baseball with an initial speed of 79.0 mi/h. Just before an infielder catches the ball at the same level, its speed is 65 ft/s. How much of the ball's mechanical energy is dissipated by air drag? (The weight of a baseball is 9 oz.)

## Homework Equations

ke=1/2mv

^{2}

ug=mgh

Emec = ΔU + ΔK

**ANSWER IS: 80.4 ft*lb**

## The Attempt at a Solution

Converting knowns to metres/second:

79.0 mi/h (0.44704) = 35.32 m/s

65 ft/s (0.3048) = 19.81 m/s

When they say "weight" do they mean

fg=9 oz. = 2.5 N

__or__

mass= 9 oz. = 0.255 kg

ΔKE=1/2mvf

^{2}-1/2mvi

^{2}

=1/2(0.255)(19.81)

^{2}-1/2(0.255)(35.32)

^{2}

=50.0356-159.0565

=-109.02 J

This is where I wasn't sure how to continue..

Any help is appreciated, thanks!