(a) with what speed must a ball be thrown vertically from ground level to rise to a maximum height of 52 m? (b) how long will it be in the air?

Explanation:

Maximum height reached by the ball, s = 52 m

Let u is the initial speed of the ball and v is the final speed of the ball, v = 0 because at maximum height the final speed goes to 0. We need to find u.

(a) The third equation of motion as :

Here, a = -g

u = 31.92 m/s

(b) Let t is the time when the ball is in air. It is given by :

t = 3.25 seconds

Hence, this is the required solution.                                                                  

second mirror gathers light from a faraway object and reflects it to another mirror. - a.

its c i just checked it