Question

The amplitude of a simple pendulum is $10cm$. When the pendulum is at a displacement of $4cm$ from the mean position, the ratio of kinetic and potential energies at the that point is:

• A. $5.25$
• B. $2.5$
• C. $4.5$
• D. $7.5$

Answer 1

Answer: (A)

$5.25$

$\frac{K.E}{P.E}=\frac{\frac{1}{2}m{w}^2(A^2-x^2)}{\frac{1}{2}m{w}^2{x}^2}$

$\frac{K.E}{P.E}=\frac{A^2-x^2}{x^2}$

$=\frac{{10}^2-4^2}{4^2}$

$=\frac{84}{16}$

$\frac{K.E}{P.E}=\frac{21}{4}=5.25$