Question

a body is projected vertically upwards with velocity u returns to starting point in 4 sec. If g=10m/s^2, the value of u is

Answer 1

$time \: of \: flight = \frac{2u}{g} = 4 \\ \frac{2u}{10} = 4 \\ u = \frac{4 \times 10}{2} = 20 \: m \: per \: second$

Answer 2

Answer:

The value of u is 20 m/s.

Explanation:

Given that,

Initial velocity = u

Time t =4 sec

For the value of u,

Using formula of time of flight

$t=\dfrac{2u}{g}$

Where,

u = initial velocity

t = time

g = acceleration due to gravity

Put the value of g and t in equation (I)

$4=\dfrac{2u}{10}$

$u = 20\ m/s$

Hence, The value of u is 20 m/s.