# Measuring heights with a stopwatch

Your goal in this experiment is to determine the height of the first, second, and third floors above the basement level in the Center for Imaging Sciences building. However, you may not use metersticks; your only tool is a stopwatch.

1. Put observers with stopwatches in place: some on the basement level, some on first floor, some on second floor, some on third floor.

2. From the basement level, I will toss a ball up into the air. The ball will go up to just above the level of the third floor, then fall back down (that's the plan, at least).

3. Observers on each level should lie down on the floor and keep a level, horizontal gaze. When the ball first passes your eyes (on its way up), start the timer. When the ball again passes your eyes (on the way down), stop the timer.

4. All observers will record the interval, and we'll write down all the values back in the classroom.

Your job is to use this measurements of TIME to figure out the DISTANCE of each floor above the basement level. You should also calculate the height of the ball at its peak, and its velocity when it strikes the floor.

If you finish early ....

Suppose that we were to repeat this experiment, with the same building and the same ball and exactly the same initial velocity .... but do it on the lunar surface. How high would the ball have gone? How long until the ball would have hit the floor? Can you figure out what times would have been measured by someone standing on each floor -- basement, first, second, and third?