1) A .145 kg baseball can be thrown at 44.7 m/s by a big league baseball pitcher with a killer fastball. That is 100 miles per hour! How much kinetic energy does that baseball have?

Question

1) A .145 kg baseball can be thrown at 44.7 m/s by a big league baseball pitcher with a killer fastball. That is 100 miles per hour! How much kinetic energy does that baseball have? 2) If you get hit by the baseball in problem 1, how much work can it do on you? 3) If the baseball in problem 1 is taken to the top of a 20 meter tall building and dropped, how fast is it travelling just before impact? 4) How much KE will the baseball in problem 3 have just before impact? 5) How much work can be done by the baseball in problem 3 upon impact?

Answer 1

1. KE = 1/2(mv^2) = 144.86 jouls
2. W = Change in KE = KEf-KEi

= 0-144.86 = 144.86 Jouls of work.

3, v^2=u^2+2gh

v= sqrt(u^2+2gh ) = 19.79m/s (u=0)

4, kE=mgh = 0.145*9.8*20 joule.

5, W= KEf-KEi = 0.145*9.8*20 joules.