Projectile vs drop: Qualitative Testing Experiment


Test whether the horizontal and vertical motions of a projectile are independent of each other.

Prior Knowledge

  1. Understanding of motion with constant velocity.
  2. Understanding of motion of falling objects.
  3. Reference frames.

Description of the Experiment

View the setup of the experiment using the first two frames. Do not view the rest. The left ball with go straight down after the release, the right ball with be shot horizontally by the spring. Use the idea that vertical motion is independent of horizontal to predict which ball lands first. Then view the experiment and decide if your prediction was correct. Make sure that you base the prediction on the explanation that worked for two observational experiments! If the outcome ofthe experiment did not match your prediction, answer the questions after the experiment.

Addtional Information

Use hypothetico-deductive reasoning to formulate your prediction:

Before Experiment is Performed


Horizontal and vertical motion of an object are independent

AND we assume that there are no air effects


Additional assumptions


We let one ball drop down and the other one shot horizontally from the same height as the first

Suggested testing experiment


We would expect that ... happens

Prediction based on explanation/rule/idea + additional assumptions about the system

After experiment has been performed

Expected outcome occurred


Expected outcome did NOT occur

Explanation/rule/idea has not yet been disproven


? ?

EITHER: We made a mistake with our assumptions, experimental set-up etc... OR Explanation/rule/idea is not valid in this regime

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  1. What was your original prediction? On what physics knowledge did you base it?
  2. If you based it on your intuition, then why do you think you failed? (If your prediction did not match the outcome of the experiment)
  3. Should you abandon your intuition in the pysics class then?
  4. How do you need to modify the reasoning behind your prediction to make sure that the predicted outcome and the real one match?