Projectile Motion... HELP ASAP!

Question

You are standing at the top of a cliff that has a stairstep configuration. There is a vertical drop of 7 m at your feet, then a horizontal shelf of 5 m , then another drop of 3 m to the bottom of the canyon, which has a horizontal floor. You kick a 0.47 kg rock, giving it an initial horizontal velocity that barely clears the shelf below. What initial horizontal velocity v will be required to barely clear the edge of the shelf below you? The acceleration of gravity is 9.8 m/s 2 . Consider air friction to be negligible. Answer in units of m/s. How far from the bottom of the second cliff will the projectile land? Answer in units of m.

Answer 1

It is advisable to break this problem into parts:

First, how long does it take to drop the distance of the shelf?

Given the time it takes to drop to the second shelve, how fast must the object go to pass the shelf in that amount of time?

Given the speed how far is it going to go if it has an additional distance to fall?

etc.

Given these smaller questions, and knowns and unknowns, what equation(s) would be useful in this problem? List the knowns and unknowns and you might be able to recognize useful equations. (Hint: you're probably already using the equation(s) a lot by this point in the class already, and algebra will be necessary)