Question

What is the velocity of the bob of pendulum at its mean position, if it is a1 to vertical height of $10cm$ ? $(g=9.8m/s^2)$

• A. 2.2 m/s
• B. 1.8 m/s
• C. 1.4 m/s
• D. 0.6 m/s

Answer 1

Answer: (C)

Total energy remains conserved in simple harmonic motion.
The bob possess kinetic energy at its mean position which gets converted to potential energy at height $h$. But the total energy remains conserved.
Hence, we have
$KE=PE$
Let velocity of bob at mean position to $v$ and $m$ be its mass, then we have
$\frac{1}{2}m{v}^2=mgh$
$\Rightarrow v=\sqrt{2gh}$
Putting $g=9.8m/s^2,h=0.1m$
$\therefore v=\sqrt{2\times 9.8\times 0.1}=1.4m/s$