Question

On an inclined plane of inclination ${30}^{\circ }$, a ball is thrown at an angle of ${60}^{\circ }$ with the horizontal, from the foot of the incline, with a velocity of $10\sqrt{3}{\text{ms}}^{-1}$. Then, the ball will hit the inclined plane in time: (take $g=10m{s}^{-2}$)

• A. $1s$
• B. $2s$
• C. $2\sqrt{3}s$
• D. $4\sqrt{3}s$

Answer 1

The correct option is B $2s$


The time of flight on an inclined plane is
$T=\frac{2v\sin \theta }{g\cos \alpha }$
$T=\frac{2\times 10\sqrt{3}\times \sin ({60}^{\circ }-{30}^{\circ })}{g\cos {30}^{\circ }}$
$=2s$