振振有词 :物体振动时便会发出声音 .隔墙有耳 :声音可以在固体、气体中传播 .立竿见影 :光在空气中沿直线传播 .孤掌难鸣 :一个物体不可能产生力的作用 .无风不起浪 :力是改变物体运动状态的原因 .顺水推舟 :如果两个分力的方向相同 ,则合力大小等于这两个分力大小之和 .叶落 The quagmire has a word: When the object vibrates, it will make a sound. The partition wall has ears: The sound can spread in solids and gases. Immediately: Light travels in a straight line in the air. Solitary palms are difficult to sing: It is impossible for an object to produce a force. No wind is not lifted: Force is to change the motion state of an object. The reason. Pushing the boat: If the two components are in the same direction, the resultant force is equal to the sum of the two component forces.