Answer:
Total time of flight is 18 s.
Explanation:
The projected stone is a projectile, so that the time required is the total time of flight (T).
T = [tex]\frac{2U Sin A}{g}[/tex]
where: U is the velocity of the stone (90 m/s), A is the angle of projection, and g is the gravitational acceleration (10 m/[tex]s^{2}[/tex]).
Then,
T = [tex]\frac{2 *90 sin 90^{o} }{10}[/tex]
= [tex]\frac{180}{10}[/tex]
= 18
T = 18 s
The time taken for the stone to travel up and back to the ground is 18 seconds.
