Speed and Acceleration (Non-Uniform Motion Lab)

Imagine taking a short trip in your car. When you first start out, you push on the gas pedal; the car starts moving and then picks up speed a you pull away. Once you reach a reasonable speed you set your cruise control and your speed then remains constant for a while. However, as you approach your destination you use the brakes to slow the car down and make it stop.

ON YOUR OWN:

Question: How could you represent the motion of your car in a way that shows how it is different in these three situations (speeding up, constant speed, slowing down)? Sketch your representations below. Think about the strobe light diagrams we created on the whiteboards in class. (or you might want to use pictures, symbols, equations, charts, etc).

SHARE:

Now share your ideas with your group members. Also, listen to their ideas and try to agree on two representations that are the most informative about what is happening to the speed of the car during each part of the trip. Draw the two representations you agreed upon below:

Collecting and Interpreting Evidence:

Question: How does a speed-time graph represent speeding-up and slowing-down?

Experiment #1

Equipment:

  • Steel Ball Bearing
  • Track
  • 3 wood blocks
  • Pencil

STEP #1:

  1. Set up your track so that it looks like the track above.
  2. Practice releasing the ball through the starting tube and letting it roll down the track.
  3. Time how long it takes the ball to reach each distance interval (50cm, 100cm, 150cm, 200cm).
  4. Once you have practiced and feel like you are timing the ball accurately, conduct 3 trials and complete the table below.

Checkpoint 1 / Checkpoint 2 / Checkpoint 3 / Checkpoint 4
__50__cm from start / _100__cm from start / _150__cm from start / _200__cm from start
Trial 1
Trial 2
Trial 3

STEP #2:

  1. Plot the data points for each of the 3 trials on the graphs below:
  2. Draw a best-fit line for the data on each graph (the line that best fits the data – NOT a zig-zag line).

What can you tell about the motion of the ball when looking at the distance vs. time graphs above for your three trials? (uniform or non-uniform, constant or changing, etc…) How do you know this? Explain your reasoning using data.

STEP #3:

  1. Sketch a line on the velocity vs. time graph below that would represent what happens to the velocity of the ball as it rolls down the track in experiment #1.

What can you tell about the velocity of the ball? (uniform or non-uniform, constant or changing, etc…) How do you know this? Explain your reasoning using data.

Experiment #2

STEP #1:

  1. Set up your track so that it looks like the track above.
  2. Practice releasing the ball through the starting tube and letting it roll down the track.
  3. Time how long it takes the ball to reach each distance interval (50cm, 100cm, 150cm, 200cm).
  4. Once you have practiced and feel like you are timing the ball accurately, conduct 3 trials and complete the table below.

Checkpoint 1 / Checkpoint 2 / Checkpoint 3 / Checkpoint 4
__50__cm from start / _100__cm from start / _150__cm from start / _200__cm from start
Trial 1
Trial 2
Trial 3

STEP #2:

  1. Plot the data points for each of the 3 trials on the graphs below:
  2. Draw a best-fit line for the data on each graph (the line that best fits the data – NOT a zig-zag line).

What can you tell about the motion of the ball when looking at the distance vs. time graphs above for your three trials? (uniform or non-uniform, constant or changing, etc…) How do you know this? Explain your reasoning using data.

How does the motionof the ball in Experiment #2 compare to the motionof the ball in Experiment #1? Explain your reasoning. Provide evidence in your answer.

STEP #3:

  1. Sketch a line on the velocity vs. time graph below that would represent what happens to the velocity of the ball as it rolls down the track in experiment #1.

What can you tell about the velocity of the ball? (uniform or non-uniform, constant or changing, etc…) How do you know this? Explain your reasoning using data.

How does the velocity of the ball in Experiment #2 compare to the velocity of the ball in Experiment #1? Explain your reasoning. Provide evidence in your answer.

Experiment #3

STEP #1:

  1. Set up your track so that it looks like the track above.
  2. Practice giving the ball a push so that it rolls up the track.
  3. Time how long it takes the ball to reach each distance interval on its way up the track. You might not be timing for ALL intervals because the ball may not reach all intervals. (50cm, 100cm, 150cm, 200cm).
  4. Once you have practiced and feel like you are timing the ball accurately, conduct 3 trials and complete the table below.

Checkpoint 1 / Checkpoint 2 / Checkpoint 3 / Checkpoint 4
__50__cm from start / _100__cm from start / _150__cm from start / _200__cm from start
Trial 1
Trial 2
Trial 3

STEP #2:

  1. Plot the data points for each of the 3 trials on the graphs below:
  2. Draw a best-fit line for the data on each graph (the line that best fits the data – NOT a zig-zag line).

What can you tell about the motion of the ball when looking at the distance vs. time graphs above for your three trials? (uniform or non-uniform, constant or changing, etc…) How do you know this? Explain your reasoning using data.

STEP #3:

  1. Sketch a line on the velocity vs. time graph below that would represent what happens to the velocity of the ball as it rolls down the track in experiment #1.

What can you tell about the velocity of the ball? (uniform or non-uniform, constant or changing, etc…) How do you know this? Explain your reasoning using data.

Experiment #4

STEP #1:

  1. Set up your track so it looks like the track above. Practice giving the ball a push so it rolls up the track.
  2. Practice giving the ball a push so that it rolls up the track.
  3. Time how long it takes the ball to reach each distance interval on its way up the track. You might not be timing for ALL intervals because the ball may not reach all intervals. (50cm, 100cm, 150cm, 200cm).
  4. Once you have practiced are timing the ball accurately, conduct 3 trials complete the table below.

Checkpoint 1 / Checkpoint 2 / Checkpoint 3 / Checkpoint 4
__50__cm from start / _100__cm from start / _150__cm from start / _200__cm from start
Trial 1
Trial 2
Trial 3

STEP #2:

  1. Plot the data points for each of the 3 trials on the graphs below:
  2. Draw a best-fit line for the data on each graph (the line that best fits the data – NOT a zig-zag line).

What can you tell about the motion of the ball when looking at the distance vs. time graphs above for your three trials? (uniform or non-uniform, constant or changing, etc…) How do you know this? Explain your reasoning using data.

How does the motionof the ball in Experiment #4 compare to the motionof the ball in Experiment #3? Explain your reasoning. Provide evidence in your answer.

STEP #3:

  1. Sketch a line on the velocity vs. time graph below that would represent what happens to the velocity of the ball as it rolls down the track in experiment #1.

What can you tell about the velocity of the ball? (uniform or non-uniform, constant or changing, etc…) How do you know this? Explain your reasoning using data.

How does the velocityof the ball in Experiment #4compare to the velocityof the ball in Experiment #3? Explain your reasoning. Provide evidence in your answer.

Write a short paragraph explaining what you have learned about non-uniform motion in this lab activity. How does the motion compare when the ball is rolled up the track vs. down and how does the motion compare with 2 blocks of height as opposed to only one? Provide evidence (data) in your paragraph that explains your reasoning.

Adapted from Physics for Everyday Thinking 20061