一块质量为 m 的木块放在地面上,用一根弹簧连着木块,如图所示,用恒力 F 拉弹簧,使木块离开地面,如果力 F 的作用点向上移动的距离为 h ,则 ( )
A.
木块的重力势能增加了 mgh
B.
木块的机械能增加了 Fh
C.
拉力所做的功为 Fh
D.
木块的动能增加了 Fh
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