CoachA mechanical wave is a disturbance propagating through a material medium — rope, water, air, rock — carrying energy without transporting matter: each piece of the medium swings briefly in place, hands the motion on, and settles back.
示例
Example 20.2 (No matter transport)
In the stadium wave the “medium” is the crowd: what travels is the act of standing up, while every spectator keeps their seat. On the pond, the ring expands but a floating cork only bobs in place.