Determine the total mechanical energy of a 250 g baseball if it has a velocity of 30 m/s when it leaves the pitcher's hand 1.2m above the ground.

There's kinetic and potential energy, and they need to be added to give the mechanical energy:

K = 1/2*m*v^2 = 1/2*0.25*30^2 = 112.5 J

U = mgh = 0.25*10*1.2 = 3J (notice that I took g = 10 m/s^2, instead of 9.81 ..., also I have assumed the common choice of U = 0 at the ground level (h=0), although what really matters are differences in height.

Total = 115.5 J.