篮球从一定高度下落至地面,经多次反弹后静止在地面上,此过程中

篮球从一定高度下落至地面,经多次反弹后静止在地面上,此过程中(  

A.动能时刻在减少               B.重力始终做正功

C.重力势能时刻在减少           D.机械能不守恒

答案

D

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