How do I calculate the trajectory of a thrown ball onto a roof?

[wolves5]

A ball is thrown from the ground onto a roof of height yroof = 15 m from a distance of x = 7 meters away as shown in the diagram to the left. The maximum height of the ball's trajectory is ymax = 4 meters above the top of the roof.

(a) Find the required initial vertical component of the velocity, Vy.

Since there's no angle, I don't know how to approach it. Usually, I would just do velocity x sin(angle) to get the answer.

(b) Find the time for the ball to reach maximum height.
(c) Find the time for the ball to fall from the maximum height to the rooftop.

(d) Find the initial horizontal component of the velocity.
I have the same problem that is similar to a. I don't know how to approach it without an angle value.

 

[ehild]

Write up the relations between x, y, vx, vy, angle, and time, see what you know and solve for the unknowns.

ehild

 

[wolves5]

This doesn't help me. I'm still confused. I just don't know how to start it.

 

[wolves5]

Actually, I got parts a and b. For a, I got 19.31 m/s. For b, I got 1.968 seconds. How do I approach c and d. I don't know which equations to use.

 

[ehild]

c. You know the displacement from the highest point of trajectory to the roof. It is free fall. Find time.

d. You know the horizontal distance. In the horizontal direction, the velocity is constant. Use the whole time of flight to get the velocity.

ehild