Question

A body projected vertically upwards with a velocity $u$ returns to the starting point in 4 seconds. If $g = 10$m/sec², the value of $u$ is

• A. 5 m/sec
• B. 10 m/sec
• C. 15 m/sec
• D. 20 m/sec

Answer 1

Answer: (D)

20 m/sec

Answer 2

Time of flight

$T = \frac{2u}{g} = 4\mspace{6mu}\sec \Rightarrow u = 20\mspace{6mu} m/s$