What it means to view something from a frame of reference.

well a frame of reference is The viewpoint from which motion is being considered. so probably like a cop with a speedometer watching cars drive by, ik i probably only got that half right but still i hoped it  helped

none, its a machine

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.