Question

A fly wheel rotating at $600rev/min$ is brought under uniform deceleration and stopped after $2minutes$, then what is angular deceleration in $rad/{sec}^2$?

• A. $\frac{\pi }{6}$
• B. $10\pi$
• C. $\frac{1}{12}$
• D. $300$

Answer 1

The correct option is A $\frac{\pi }{6}$

Initial angular speed $w_0=2\pi \times \frac{600}{60}rad/s=20\pi$

From the laws of rotational kinematics

$w=w_0+\alpha t$

where $w$ is final angular speed $\alpha$ is acceleration/deceleration $t$ is time.

$0=20\pi +\alpha \times (2\times 60)$

Left hand side is zero because the fly wheel is stopped.

minus sign shows it is deceleration

$\therefore 20\pi +120\alpha =0\Rightarrow 120\alpha =-20\pi \Rightarrow \alpha =\frac{-20}{120}\pi \Rightarrow \alpha =\frac{-\pi }{6}$