Harold the Hurler is a physics student who is renowned for his baseball pitching

Question

Harold the Hurler is a physics student who is renowned for his baseball pitching arm. In order to determine the amount of work he performs in throwing a baseball, Harold devises an experiment. He stands at the bottom of a deep pit and hurls a 0.144-kg baseball through an open third-floor window in a nearby building. Harold's aim is so accurate that the ball then smoothly enters the tube of the Baseball Absorber that Harold invented and patented. In this device the ball compresses a spring until it comes momentarily to rest, and this maximum amount of compression is recorded as 0.493 m. The spring's force constant is 887 N/m, and the position of the baseball's momentary rest is 7.23 m above ground level. The point in the pit where the Hurler starts his pitch is 11.7 m below ground level. How much work does Harold perform on the baseball? Take g = 9.80 m/s2.

Explanation / Answer

Using work energy theorem,

work done by harold + work done by gravity + work done by spring = change in KE

W + ( - 0.144 x 9.81 x (7.23 + 11.7) ) + ( - 887 x 0.493^2 /2 ) = 0 - 0

W = 134.53 J

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