1. A stone is thrown vertically upward from the ground and just reaches the top of a building 100m high. At the same instant that the stone is thrown from the ground a ball is dropped from rest at the top of the building. At what height do the stone and the ball pass one another. (answer: 75m above ground)

Given:

Stone

Is this velocity actually given? Do I only state a given velocity of 0m/s if "rest" or "stationary" is mentioned?

Ball

Required:

ball and stone meet = ?

Analysis:

Solve for time first.

Ball

Stone

Determine the height at which they meet.

Ball

Verify with stone equation

Solve:

Ball

Stone

Sub ball equation into stone equation

What do I do next? I think I've made an error with the given 's, but I'm not sure how.