Question

A flywheel starts from rest and rotates at a constant acceleration of $2rad\cdot s^{-2}$. The number of revolutions that it makes in first ten seconds is

• A. 16
• B. 24
• C. 32
• D. 8

Answer 1

Answer: (A)

Initial angular velocity of flywheel, ${\omega }_0=0$
Angular acceleration, $\alpha =2rad/s^2$
Angular displacement in $t=10s$ is given as
$\theta ={\omega }_{0}t+\frac{1}{2}\alpha t^2$
$=0\times 10+\frac{1}{2}\times 2\times 10^2$
$=100rad$
Number of revolution $=\frac{\theta }{2\pi }=\frac{100}{2\pi }$
$=\frac{100}{2\times \frac{22}{7}}$
$=\frac{700}{44}=15.9\sim eq16$