Question

A girl is swinging in the park. Which of the following quantities will remain constant for her throughout her motion?

Answer 1

Mechanical energy (total energy) of the object = Potential energy + Kinetic energy
When the girl is swinging at the extreme points, her Kinetic energy will be zero, as she’ll stop there.
As she reaches the lowest point, the Potential energy will be zero as it is the reference we are considering.
As she is moving from one extreme point to the mean position, the potential energy will keep decreasing and the kinetic energy will be increasing as the velocity is increasing. Similarly, from mean position to other extreme position $\text{PE}$ will increase and the $\text{KE}$ will decrease and become zero at the extreme point but, the total energy will remain the same throughout the cycle.