Motion with Constant Acceleration

Purpose: To investigate the motion of objects sliding down an inclined ramp.


  • To verify that the acceleration of a sliding object is the same regardless of whether it is sliding up or down a frictionless ramp.
  • To determine how the slope of the ramp affects the acceleration with which objects slide up or down.
  • To learn how to measure acceleration using photogates, Pasco Interface, and the Data Studio software.


  • Air track
  • Photogate connected to PASCO Interface
  • Glider with picket fence
  • Spacers
  • Calipers


When objects slide along ramps their velocity changes, and thus we say they experience acceleration. The acceleration turns out to depend on how steep the ramp is, but not on whether the objects are sliding up or down.

If we have an initially level ramp, and we put a spacer with height h under one of its supports, its slope is determined by that spacer and is equal to:

     acceleration = g × (Height of spacer)/(Distance between supports)

We will use four spacers with similar height. The distance between the supports is 100 cm.

Experiment, Data and Results

Preliminary Setup
  • Level the air track. Place the glider with the picket fence on the air track while the air pump is on. It should not drift in any direction. If it drifts, adjust the height of the supports.
  • Photogate and Computer Set up. Follow the Picket Fence and Photogate Instructions to set up the computer.
  • Create slope. Put one spacer under one of the supports of the air track.
  • Photogate Check. As the glider with the picket fence glides along the ramp, the photogate must blink exactly once for each time when a darkened space goes through it.
Activity 1:

We will measure the acceleration of the glider once at it slides up and once as it slides down the track.

    • Place the glider on the track lower than the photogate.
    • Turn on the Air Pump and click on Start the experiment.
    • Give the glider a push upward. The photogate will measure how fast each of its darkened segements go through it, and will send that information to the computer, where the compute rwill perform the calculations and will give the measured acceleration of the glider.
    • Stop the experiment once the glider has passed through the photogate.
    • Repeat the steps, but this time, place the glider above the photogate and let it slide down on its own.
    • Write down your results in the following table.
  Direction   acceleration [m/s2]



Compare your results with the results of the other teams?

Do they agree or disagree?

Write down the average value for the acceleration measured by everyone:

Calculate the acceleration according to the formula given in the Theory section.

Do the experimental and theoretical value agree?

Activity 2:

We will measure the acceleration for different slopes.

  • Add another spacer under the airtrack’s support.
  • Check whether the photogate blinks properly. Remember, it must blink exactly once for each time when a darkened space goes through it.
  • Place the glider with the picketfence above the photogate.
  • Turn on the air pump and start the experiment. After the glider goes through, stop the experiment and turn off the air pump.
  • Repeat for two and three spacers.
  • Write down the results for the acceleration in the following table:
      Number of Spacers   acceleration [m/s2]

According the to the theory, what happens to the acceleration if you double the height of the spacer? What if you triple the height?

According to your measurements, what happens to the acceleration if you double the number of spacers?What if you triple the height?

Do your results agree with the theory?