Question

A pendulum of mass m kg and length $l$ m is released from rest at angle $\theta ={30}^{\circ }$ with the vertical. The power delivered by all the forces acting on the bob at angle $\theta ={15}^{\circ }$

• A. Must be positive
• B. Must be negative
• C. May be zero
• D. May be negative

Answer 1

The correct option is D May be negative

Power is positive if speed is increasing and vice versa.

Speed is decreasing, power is negative

Speed is increasing, power is positive