Physics Lab

Motion of a Motorized Cart

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Purpose:

Equipment:

constant velocity motorized cart

meter stick or metric tape

about 2 meters of ticker tape

graph paper

masking tape

stopwatch or watch with a seconds hand

data table

grading rubric

Description:

In this lab you will observe and measure the motion of a motorized cart by marking its position along a strip of tape at regular time intervals. Note that you can adjust the speed of the cart using the small dial - find a speed that works well for you and then do not change the cart's speed during the experiment.

Once you have a record of the cart's motion, you can measure and record its position in a data table and construct a position vs. time graph for the cart's motion. You can then calculate the displacement and average velocity of the cart during each time interval, and construct a velocity vs. time graph for the motion.

Although you will work as a team during this lab, each student will turn in their own lab report.

Here is the rubric for this lab.

Procedure:

Setup:

  1. Fasten a 2-meter strip of ticker tape to your lab table with masking tape.
  2. Place the motorized cart beside the tape, near one end. Mark the cart's starting position on the tape.
  3. Adjust the speed of the cart so that it takes at least 30 seconds for the cart to move the length of the tape.

Taking the Data:

  1. There are 3 jobs:
    1. one person's job is to release the cart at the start of the run
    2. a second person marks the position of the cart on the ticker tape
    3. the third person watches the clock and calls out regular (5 second intervals might be convenient) time intervals.
  2. You may want to make a couple of practice runs in order to get everyone coordinated, and remember that the tape has another side if you mess it up. When you are ready, release the cart and record its positions.

Analysis:

  1. Use a meter stick or metric tape to measure each position of the cart (measured from the start). Record your data in the data table.
  2. Plot each position/time data pair on your position vs. time graph.
    1. The position vs. time graph is already titled, and the time axis has been labeled. You need to select a position scale that creates the largest convenient graph that accommodates your data, and label the position axis.
    2. Draw the straight line (use a straight edge) that best fits your data points. DO NOT "connect the dots".drawing a graph
  3. Calculate and record the displacement (ending position - starting position) of the cart during each time interval.
  4. Calculate and record the average velocity (displacement/time) of the cart during each time interval.
  5. Plot each velocity/time data pair on your velocity vs. time graph.
    1. The velocity vs. time graph is already titled, and the time axis has been labeled. You need to select a velocity scale that creates the largest convenient graph that accommodates your data, and label the velocity axis.
    2. Draw the straight line (use a straight edge) that best fits your data points. DO NOT "connect the dots".
  6. Calculate the slope of the position vs. time and velocity vs. time graphs. Show your calculation.

Results and Conclusions:

  1. How do successive displacements of the cart compare? Why?
  2. What is the slope of the position vs. time graph? What is the significance of this value?
  3. How would the position vs. time graph be different if the cart had gone faster or slower?
  4. What is the slope of the velocity vs. time graph? What is the significance of this value?
  5. Was the velocity of the cart more-or-less constant during its motion? How do you know?
  6. How would the velocity vs. time graph be different if the cart had gone faster or slower?
  7. What was the acceleration of the cart during its motion? How do you know?
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last update November 22, 2005 by JL Stanbrough