Help Needed: Solving Homework Equations Without Enough Variables

[krash91]

Hey guys, I'd love some help with these problems, its seems to me that there aren't enough variables.

Homework Statement

A .145kg baseball leaves a pitcher's hand at a speed of 35 m/s. If air drag is negligible, how much work has the pitcher done on the ball by throwing it?

Homework Equations

W=FD

The Attempt at a Solution

W=(MA)(VT)

Seems like I can't solve it without the time it was in the air.

And this one as well

Homework Statement

Find the force needed for friction in the tires of a 2000lb car to stop it in 100ft

Homework Equations

W=FD?

The Attempt at a Solution

Again, it seems like there aren't enough varibles. If I had the velocity of the car then it would make sense.

Some hints and nudges in the right direction would be great!

 

[tiny-tim]

welcome to pf!

hey krash91! welcome to pf!

for both questions, use the work energy theorem …

what do you get? ​