Q. A stone is thrown with an initial speed of $4.9\ m/s$ from a bridge in vertically upward direction. It falls down in water after $2\ sec$. The height of the bridge is
A) $4.9\ m$
B) $9.8\ m$
C) $19.8\ m$
D) $24.7\ m$
Explanation
(b) Speed of stone in a vertically upward direction is $4.9\ m/s$. So for vertical downward motion we will consider $u = - 4.9\ m/s$
$h = ut + \frac{1}{2}gt^{2} = - 4.9 \times 2 + \frac{1}{2} \times 9.8 \times (2)^{2} = 9.8\ m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.