A ball is projected upward at time t = 0.0 s, from a point on a roof 90 m above the ground. The ball rises, then falls and strikes the ground. The initial velocity of the ball is 36.2 m/s if air resistance is negligible. The time when the ball strikes the ground is closest to

The time when the ball strikes the ground is closest to  

Explanation:

From the question we are told that

  The time of projection is t = 0.0 s

   The  distance of the point  from the ground  is  

    The  initial velocity of the ball is  

generally the time required to reach maximum height is  

Where is the acceleration due to gravity  with value  

Substituting values

when returning the time and velocity at the roof level is  t =  3.69 s and  u = 36.2 m/s this due to the fact that  air resistance is negligible

   The final velocity at which it  hit the ground is

So  

substituting values

The time taken for the ball to move from the roof level to the ground is  

substituting values

The total time for this travel is  

explanation:

v=uf/(u-f)

= 5.-10/(5+10) convex lens has negative focal length