Balloon in a cart: Testing Experiment


To predict what happens to a balloon in a cart when the cart is pushed forward.

Description of the Experiment

  1. A helium-filled balloon is attached to a thread and placed inside a clear plastic box. The box is on wheels. Predict what happens to the balloon when Dave pushes the cart forward. Do not play the movie.
  2. Explain how you made the prediction and write it down. What physics principles did you use?
  3. Play the movie. Was your prediction correct? If not, what do you need to modify to account for the results of the experiment?
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. What physics models did you use to make the original prediction?
  2. What limitations of the models did you need to take into account to explain the result of the experiment?
  3. What information about the box could have been helpful at the beginning?