Being able to use the law of conservation for energy makes physics problems a lot easier. One way that we say that energy is conserved in rotational motion is by saying the object is "rolling without slipping". This is the same as when we said "a frictionless surface" in linear kinematics. For rotation we need friction to make the object rotate but when the object doesn't slip in relation to the surface then there is no work done by the friction force and energy is therefor conserved. We will look at 2 examples in this video as well If there is a topic you want me to do leave them in the comments below. #physicstutor #rollingwithoutslipping #conservationofenergy