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The hammer throw is a track-and-field event in which a 7.8-kg ball (the \'\'hamm

ID: 2007477 • Letter: T

Question

The hammer throw is a track-and-field event in which a 7.8-kg ball (the ''hammer''), starting from rest, is whirled around in a circle several times and released. It then moves upward on the familiar curving path of projectile motion. In one throw, the hammer is given a speed of 26.0 m/s. For comparison, a .22 caliber bullet has a mass of 2.6 g and, starting from rest, exits the barrel of a gun with a speed of 409 m/s. Determine the work done to launch the motion of both the hammer and the bullet.

Explanation / Answer

Work done W = change in k.e.

= Kf   - Ki

since both hammer and bullet started from rest, Ki would be zero in both cases. hence

W = Kf =   (1/2) * m * vf2

for the hammer Wh  = (1/2) * 7.8 * 26.02

= 2.6364 * 103   J

for the bullet     Wb  = (1/2) * 2.6 * 10-3 * 4092

= 2.1746 * 102   J

I typed 103 in place of 102, my mistake.