Galileo's Mast Experiment: Qualitative Testing Experiment


Test the idea that motion in the horizontal and vertical directions are independent of each other.

Prior Knowledge

  • Reference frames.
  • Relative motion

Description of the Experiment

David will skate across the floor after pushing off once (his pace does not change after he starts moving) and then drop the ball that he is holding in his hand. Use the explanations you invented for the first experiment (ball and cart) to predict where the ball will land relative to David before you view the video.

Addtional Information

Think of how the ball will move with respect to David and how it will move with respect to the floor.

Youtube movies can be stepped frame by frame using the , and . keys on your keyboard. If you want to download the movie to your computer, right-click or control-click HERE.


  1. Did the outcome of the experiment match your prediction? If it did not, how should you revise the reasoning that led to the prediction?

  2. What would happen if David moved faster but with constant pace?

  3. What would you see if you were in a reference frame moving parallel to David with the same pace?

  4. What would you see if you were standing on the floor and David kept pushing off the floor after he released the ball?