Q. A body projected vertically upwards with velocity $u$ returns to the starting point in $4\ $seconds. If $g = 10\ m/\sec^{2}\ $, the value of $u$ is
A) $5\ m/sec$
B) $10\ m/sec$
C) $15\ m/sec$
D) $20\ m/sec$
Explanation
(d) Time of flight $T = \frac{2u}{g}4\sec \Rightarrow u = 20\ m/s$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.