Answer
18.9rad
Work Step by Step
The formula to be used here is:
$\omega_{f}^{2} = \omega_{o}^{2} + 2\alpha(\theta-\theta_{o})$
By arranging the equation, we make $(\theta-\theta_{o})$ the subject of formula:
$(\theta-\theta_{o}) = \frac{\omega_{f}^{2}-\omega_{o}^{2}}{2\alpha}$
Substituting the values in formula and solving:
$(\theta-\theta_{o}) = \frac{0^{2}-(12.6)^{2}}{2\times (-4.2)}$
$(\theta-\theta_{o})=18.9 $ $rad$
