HL 3:   What Factors Determine Free-Fall Time?




Sky-divers and bungee-jumpers enjoy a few moments of free-fall time before their falling rates are braked by a bungee cord or a parachute. How would you characterize the motions of freely falling objects? The tennis ball in the stroboscopic picture fell to the ground in 0.5 second. The images record the tennis ball during its free-fall every 0.1 seconds. What can you say about the tennis ball's motion from the stroboscopic picture? Was the speed constant? Would a tennis ball filled with fishing weights fall at the same rate as a hollow tennis ball?



  1. To investigate the factors (variables) that affect the time it takes for an object to fall freely to the ground.

  2. To understand the kind of motion objects undergo when falling freely to the ground.


             tennis balls, hollow and
             filled with fishing weights		             coffee filters, various
            Styrofoam plates  


  1. With your group discuss a working model that would answer the question: What Factors Determine Free Fall Time?

  2. Plan and perform experiments taking into consideration the distance of the fall, and how you will drop the objects.

  3. Record notes in our lab books, and discuss your results and conclusions with your group.

  4. Complete and submit your report to your lab instructor.


  1. Complete the Working Model Form addressing the question: What Factors Determine Free-Fall Time?

  2. List the independent variables in your experiments,and explain your reasoning in each case.

  3. List the dependent variables in your experiments, and explain your reasoning in each case.

  4. How would the experiments you performed be different, if at all, if done on the Moon?

  5. In the experiments you performed, did it matter how large a distance the objects fell? Explain your answer?

  6. Did the tennis balls fall with uniform accelerated motion? Explain your reasoning.

  7. When dropped from the same height, does the mass or the surface area of an object matter more in determining the free-fall time? Explain your reasoning.


Click here to create your lab report

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