Simultaneous splat

Some graduate students decide to make headlines in the Tallahassee Democrat by dropping watermelons from the 7th floor of the Keen building, which is at a height of 24 m. The resulting explosions of the watermelons are really fun to watch. Someone decides it would be fun to try and throw a watermelon straight down from the 7th floor, and simultaneously drop a watermelon from the walkway on the second floor, at a height of 4 m, and see if they can have them simultaneously splat on the ground by landing at the same time.

(a) Draw a motion diagram for the motion of the two watermelons.

(b) Make a pictorial model for the motion of the two watermelons.

(c) What is the velocity of the watermelon dropped from the second floor when it reaches the ground?

(d) With what velocity should the student on the 7th floor throw her watermelon downward so that it reaches the ground at the same time as the watermelon dropped from the second floor?

(e) What is the velocity of the watermelon thrown from the 7th floor when it reaches the ground?

For each step (c)-(e), try to work in symbols as much as possible, substituting numbers for these symbols only at the very end.