一铅球运动员,奋力一推将8 kg的铅球推出10 m远.铅球落地后将地面击

一铅球运动员,奋力一推将8 kg的铅球推出10 m远.铅球落地后将地面击出一坑,有经验的专家根据坑的深度形状认为铅球落地的速度大致是12 m/s.若铅球出手时的高度是2 m,求推球过程中运动员对球做的功大约是多少?

答案

解析:设铅球出手时的速度大小是v0,对铅球从出手到落地这一过程运用动能定理,在这一过程中只有重力对铅球做功,所以有mgh=.

对运动员抛铅球的过程应用动能定理,人对球做的功认为是力对铅球的合功,则W=-0==-mgh=(×8×122-8×10×2)J=416 J

答案:416 J.

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