Question

A stone is thrown vertically upwards with a speed of 40m/s.The time interval for which the particle was 40m above the ground is (g=10m/s^2)

(1) 4(root 2) seconds
(2) 8 seconds
(3) 2(root 2) seconds
(4) 4 seconds

Please explain the entire answer.

Answer 1

Answer:

4) 4seconds

Explanation

v=40m/s

t=?

s(h)=40m

g=10m/s^2

according to equation of motion

s=ut+1/2at^2----eq1

substituting in eq1

40=0*t+1/2*+10*t^2

40=5t^2

t^2=40/5

t^2=8

t=√8

t=4 seconds