Which of the diagrams shown in the figure represents the variation of to mechanical energy of a pendulum oscillating in the air as a function of time.
 

1. 2.
3. 4.

(c) Hint: Apply the concept of work-energy theorem.

Step 1: Find the work done by the resistance due to air.

When a pendulum oscillates in air. it will lose energy continuously in overcoming resistance due to air. Therefore, the total mechanical energy of the pendulum decreases continuously with time.

The variation is correctly represented by a curve (c).