误解一:物体没有做功,说明它不具有机械能.分析:判断一个物体是否具有机械能,关键是要看它能不能做功,而不是看它是否正在做功.比如,被举起的锤子虽然没有做功,但它具有重力势能,下落可以做功——把钉子打进木头.所以,没有做功的物体,不一定没有机械能.误解二:物体的动能减小, Misconception 1: The object does not do work, indicating that it does not have mechanical energy. Analysis: To determine whether an object has mechanical energy, the key is to see if it can do work, rather than see if it is doing work. For example, although the lifted hammer did not do work, But it has gravitational potential energy, and the drop can do work—the nails are thrown into the wood. Therefore, an object that does not do work does not necessarily have no mechanical energy. Misunderstanding 2: The kinetic energy of the object decreases.