Calculating Force Exerted on a Baseball by a Pitcher

[physics1234]

A baseball pitcher throws a ball straight up into the air at a speed of 21.0 m/s. In the process, he moves his hand through a distance of 1.40 m. If the ball has a mass of 0.150 kg, find the force he exerts on the ball to give it this upward speed.

My problem is that I don't know where to use the 1.40m. I assume I have to find the acceleration somehow and then plug it into F=ma but every method I try seems to fail. Thanks for the help.

 

[Doc Al]

What have you tried? You have the initial and final speed and the distance; that's all you need to find the acceleration. (You may need to review your kinematic equations.)

 

[physics1234]

I used V^2=Vo^2 +2a(delta)x

and found acceleration to be 157.5.

then i used F=ma= (.150)*(157.5) abd got the answer to be 23.625. Apparently this is within 10% of the correct answer but not quite right. Any ideas what's wrong?

 

[Doc Al]

You are asked to find the force the pitcher exerted on the ball. You calculated the net force. What other force acts on the ball?