Question

A string is wrapped around the rim of a wheel of moment of inertia $0.20kg-m^2$ and radius $20cm$. The wheel is free to rotate about its axis initially the wheel is rest. The string is now pulled by a force of $20N$. The angular velocity of the string after $5$ seconds will be :

• A. $90rad/s$
• B. $70rad/s$
• C. $95rad/s$
• D. $100rad/s$

Answer 1

The correct option is D $100rad/s$

torque=T$\times r=I$$\alpha$

$20\times 0.2=0.2$$\alpha$

$\alpha =20$

$\omega =\alpha t=20\times 5=100rad/sec$