Question

For a simple pendulum, a graph is plotted between its kinetic energy (KE) and potential energy (PE) against its displacement $d$. Which one of the following represents these correctly?
(graphs are schematic and not drawn to scale)

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

In an SHM, variation of potential energy with displacement $d$ is given by
$PE\left(y\right)=\frac{1}{2}k{d}^2$, which represents the equation of a straight parabola with vertex at $d=0$.

And variation of kinetic energy with displacement $d$ is given by
$KE\left(y\right)=\frac{1}{2}k(a^2-d^2)$, which represents the equation of an inverted parabola with vertex at $d=a$.

Here, $a$ is the amplitude of the SHM.
Hence the correct choice is B.