Falling Beach Ball and Golf Ball*

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Falling Beach Ball and Golf Ball*: Testing Experiment

Aim

To revise your explanations and assumptions in the light of new evidence.

Prior Knowledge

Kinematics: All types of motion
Representation skills: Free body diagrams, motion diagrams etc.
Fluid mechanics and bouyant force.
Notions about friction.

Description of the Experiment

Below are two videos. One is a video of a golf ball falling, the second is a video of a beach all falling. Predict which ball will fall faster and explain what you are basing your prediction on. Then check the movies, timing how long each ball takes to fall, say, 1 meter. Is your prediction confirmed?

Secondly, predict what type of motion each ball will have (motion with constant speed/motion with constant acceleration/motion with changing acceleration) using the same idea/explanation on which you based your above prediction. Now check this prediction by taking frame by frame data from each video. Plot position versus times graphs and average velocity versus time graphs for each. Did your prediction match the outcome of the experiment? If not, come up with an explanation for what you see.

Addtional Information

*This experiment was suggested by Raphael Littauer.

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.