University of Virginia
Physics Department

## Galileo's Gravitational Experiment

A Physical Science Activity

### Student Activity

Materials

 Protractor Golf ball Stopwatch Tennis ball Marble Basketball Meter stick Baseball Styrofoam ball Wooden board (2 m long) with a recessed groove to fit the marble, or a plastic car racetrack with raised edges

Procedure

Part 1

1. Lay the wooden board on the table. Using the protractor to measure the angle, raise the board 5° from the table. Appoint one partner to hold the board and release the marble, and another to act as a timer.
2. Place the marble in the groove at the top of the board and release. Use the stopwatch to record the time it takes for the marble to reach the bottom. Record this in the data table.
3. Using the protractor, raise the board to 10° from the table. Release the marble from the top, and record the time.
4. Repeat this procedure for the following angles: 15°, 20°, 25° and 30°. Record your results.

Part 2

1. Station one member of your group at a surface at least 2 m from the ground; the higher the distance, the better (ask your teacher for specific instructions).
2. Station a second member on the ground directly below with a stopwatch.
3. From the high surface, release the golf ball. Record the time it takes for it to reach the ground.
4. Repeat this with the tennis ball, basketball, baseball and Styrofoam ball. Record your results on the data table.

Data Sheet

Part I:

 Angle Distance Time (seconds) Final velocity (2D/t) Initial Velocity Acceleration (Final velocity/time) 5° 0 m/s 10° 0 m/s 15° 0 m/s 20° 0 m/s 25° 0 m/s 30° 0 m/s

Part 2:
 Type of Ball Distance (m) Time (s) Final Velocity (2D/t) Acceleration (Final Velocity/time)

Questions

1. What relationship did you find in Part I between the acceleration of the ball and the angle of the wooden board? Explain this in terms of the gravitational force.

2. In Part II, did all of the balls reach the ground in approximately the same time? Were their acceleration values comparable? Explain.

3. How did the results for the Styrofoam ball compare to the others? Can you account for this difference?