Question

When does the velocity become zero ?

• A. 0.7 s
• B. 0.6 s
• C. 0.5 s
• D. 0.3 s

Answer 1

The correct option is A 0.7 s

Taking the derivative of the angular displacement $\theta$ we get the angular velocity $\omega$ which we equate it to zero.
$\frac{d\theta }{dt}=250-40t-450t^2=0$
or
$45t^2+4t-25=0$
or
$t=\frac{-4\pm \sqrt{16+4500}}{90}=\frac{63}{90}=0.7s$