Lemon falling at a constant speed from a tree with no air resistance, draw a free body diagram

Since the lemon is falling without any air resistance, the only force acting on the lemon is the acceleration due to gravity.

But, since we know that the lemon is falling with a constant speed. There has to be another unknown  force to balance the gravitational force. Which has been shown in the freebody diagram

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.