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 0.147-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 0.451 m. The spring's force constant is 847 N/m, and the position of the baseball's momentary rest is 7.49 m above ground level. The point in the pit where the Hurler starts his pitch is 13.5 m below ground level. How much work does Harold perform on the baseball? Take g = 9.80 m/s2.

Explanation / Answer

work done performed by the person on the baseball is,

            W = mg(h1+h2) + 1/2 kx2
         = (0.147 kg)(9.8 m/s2)(13.5 m + 7.49 m)+(1/2)(847 N/m)(0.451 m)2

                  = 116.378 J

                   = 116.4 J             (approximately)

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