拉力做功,
There is a soft chain of mass M and length L,its 4/5 is set on the smooth table surface,and the remainder is free in air.Then the work done in order to draw the remainder up to table is__________at least.
利用外力做功等于系统机械能的改变系统机械能的改变,我算的答案是1/5M*g*L,但感觉答案是不是太简单了点哦,不像大学物理啊.
是不是我想错了?给个简单的思路或者过程.