Question

A particle of $2g$ is initially displaced through $2cm$ and then released. The frictional force constant due to air on it is $12\times {10}^{-3}N/m$.
The restoring force constant is $50\times {10}^{-3}N/m$.
If it is oscillatory motion,its time period is:

• A. $\pi sec$
• B. $\pi /2\sec$
• C. $2\pi /5\sec$
• D. $4\pi \sec$

Answer 1

The correct option is C $2\pi /5\sec$

Constant force is not connected
$k=50\times {10}^{-3}N.m$
$m=2g$ or $\frac{2}{1000}k.g$
$T=2\pi \sqrt{\frac{m}{k}}=2\pi \sqrt{\frac{2}{1000\times 50\times {10}^{-3}}}$
$T=\frac{2\pi }{5}$