Question

Figure shows the kinetic energy $K$ of a simple pendulum versus its angle $\theta$ from the vertical. The pendulum bob has mass 0.2 kg. The length of the pendulum is equal to $(g=10m/s^2)$.

• A. $2.0m$
• B. $1.8m$
• C. $1.5m$
• D. $1.2m$

Answer 1

Answer: (C)

$1.5m$

$\frac{1}{2}m{V}_m^2=15\times {10}^{-3}$

$⟹V_m=\sqrt{0.150}m/s$

$A\omega =\sqrt{0.150}m/s$

$⟹L.{\theta }_m.\sqrt{\frac{g}{L}}=\sqrt{0.150}m/s$

$\sqrt{gL}=\frac{\sqrt{0.150}}{100\times {10}^{-3}}⟹L=\frac{0.150}{0.1}=1.5m$