Astone is thrown upward from the top of a building at an angle of 30° to the horizontal and with an initial speed of 20 m/s. the point of release is 45 m above the ground. how long does it take for the stone to hit the ground? what is the stone's speed?

Explanation:

Given

inclination

initial speed

Point of release is 45 m above the ground

Considering stone to be a projectile, so time taken by projectile for its zero vertical displacement is

Now after completing zero vertical displacement , stone needs to travel another 45 m in downward direction with initial speed u=20\sin 30

where,

thus total time time required is

vertical velocity just before hitting

Horizontal velocity

Net velocity Just before hitting