Hi, For a long time, it is always unclear for me to understand that there is a tension force acting in the slack side of a belt drive. Tension acting in the tight side is quite straight forward and hence no doubt! When I see a belt drive in motion, I always see the slack side kind of deformed and wobbling. This leaves me an impression that there is no force on that portion of belt. But in all our text books it is said that there is a tension acting. Can you explain the easiest way to understand this? May be with some examples or videos? Thanks.