Question

A pendulum has 366 J of potential energy at the highest point of its swing. How much kinetic energy will it have at the bottom of its swing?

Answer 1

968 j or kg because it cannot lose any of it energy and cannot gain any extra mass from nothing

Answer 2

Energy can neither be created nor destroy, it can only be transformed from one form to another form.
The potential energy possessed by the pendulum can not be destroyed, neither can more energy be added to it, but it can be converted from potential energy to kinetic energy.
So, at the bottom of the swing, the kinetic energy of the pendulum is going to be 366 J.