By Kate Allaway
Andy Pettitte has pitched for the Yankees for a total of 12 years and in that time has been an all-star 3 times and has won numerous awards. He is also major league baseball’s all time wins leader in the post season with 19 post season wins. Pettitte throws a four-seam fastball, a cutter, a curveball, a sinker, a changeup, and a slider.
Here I will look at his fastball and determine the force it exerts on a baseball bat.
His fastballs typically have a speed of 91 mph, or 41.7 m/s.
Vo = 0 m/s
Vf = 41.7 m/s
Distance from pitcher’s mound to home plate = 18.39 m
Vf 2= vo2 + 2a(Δx)
(41.7 m/s)2 = (0 m/s)2 + 2a(18.39 m)
a = 47.3 m/s2
mbaseball= 145g = 0.145 kg
Fexerted by baseball=(0.145kg)(47.3 m/s2)=6.9 N
Would this force break a (stationary) bat?
Ultimate (shear) strength of the wood of a bat=5x106 N/m2
Estimate that about a circle with a radius of 1 cm (A= 3x10-4 m2) of the ball comes in contact with the bat
Stress = (6.9 N/3x10-4 m2) = 23,000 N/m2