A stationary body is acted upon by a number of forces. State condition which must be applied if it doesn't rotate

correct it is c.) b b

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.

it doesn't. it was imagined up in the middle ages.