Question

A disc spinning at the rate \(27.5\ \text{rad s}^{-1}\) is slowed at the rate \(10\ \text{rad s}^{-2}\). The time after which it will come to rest is

• A. \(2.75\) s
• B. \(5.5\) s
• C. \(1.25\) s
• D. \(3.5\) s
• E. \(6.2\) s

Hint:

For rotational deceleration, the equation is exactly like linear motion: \[ \omega=\omega_0+\alpha t \]

Answer 1

The Correct Option is A

Use: \[ \omega = \omega_0 + \alpha t \] At rest: \[ \omega=0 \] \[ 0=27.5-10t \] \[ 10t=27.5 \Rightarrow t=2.75\text{ s} \] Hence, \[ \boxed{(A)\ 2.75\text{ s}} \]