Question on a problem

Le

Hi,
A batter hits a baseball 1.2 meters above the ground (the point of impact). The ball has mass m = .14g
Speed V(initital) before the ball hit the bat is 40 meters/sec. The bat does 70 Joules of work on the ball in hitting it. Find the speed of the ball after the ball leaves the bat. The ball reaches a height of 25 meters above the point of impact.
Thank you,
Le

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Pandemonium

Speed V(initital) before the ball hit the bat is 40 meters/sec.
In which direction? Down, I presume? And also, I assume that air resistance is negligible.

From the data given, I just need the mass of the baseball, the gravitational acceleration, and the height it reached. Then, just use the Conservation of Energy. The part before the ball being whacked by the bat is not important at all.

HallsofIvy

Homework Helper
[/quote]The part before the ball being whacked by the bat is not important at all.[/quote]

Yes, it is. The problem says " The bat does 70 Joules of work on the ball in hitting it." and so ADDS 70 Joules to the kinetic energy the ball already had. You use the speed of the ball before the hitting the bat to find its kinetic energy then and add 70 Joules.

Rocksicle

Originally posted by Pandemonium
I just need the mass of the baseball, the gravitational acceleration, and the height it reached.
Isn't acceleration due to gravity 9.8ms^2?

And he says that the mass is .14kg and the height reached is 25m + 1.2m

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