Constant Velocity Graphing Lab
Purpose
When forces are balanced, the motion is constant. This can be shown in both free body diagrams as well as position versus time graphs. This activity will explore both.
Background
Videos can be a useful way to track the motion of an object. Time is measured in the frame rate of the video. A typical frame rate is 30 frames per second (fps). This means that 1/30 of a second passes when a frame is advanced. Velocities can be found by knowing the distance and the time.
Procedure
Introduction Video
Use the front end of the buggy as a reference point on the scale to find the distance. Advance the video 5 frames and fill in the data table with the distances for the times. Create a graph with a spreadsheet and find the slope of the line of best fit.
Frame # | Time (s) | Distance (cm) |
1 | 0 | |
6 | 5/30 | |
11 | 10/30 | |
16 | 15/30 | |
21 | 20/30 | |
26 | 25/30 | |
31 | 30/30 | |
36 | 35/30 | |
41 | 40/30 | |
46 | 45/30 |
Questions
- What forces are acting on the buggy in this video?
- Draw the free body diagram.
- What does the slope of a position vs. time graph tell you?
- How does the motion of the buggy compare to the slope and the free body diagram?
Blue Buggy
Cue or advance the video to the point at which the buggy begins to move forward. Record the distances again using the front of the buggy as a reference. Again, advance the video 5 frames between data points. After the data has been collected, create a new graph on a new tab of the spreadsheet and find the slope. (Note: The video may play upside down, but treat it as right-side up.)
Frame # | Time (s) | Distance (cm) |
1 | 0 | |
6 | 5/30 | |
11 | 10/30 | |
16 | 15/30 | |
21 | 20/30 | |
26 | 25/30 | |
31 | 30/30 | |
36 | 35/30 | |
41 | 40/30 | |
46 | 45/30 |
Questions:
- What forces are acting on the buggy in this video?
- Draw the free body diagram.
- What does the slope of a position vs. time graph tell you?
- How does the motion of the buggy compare to the slope and the free body diagram?
Red Buggy
Repeat the same procedure from the blue buggy except advance 3 frames instead of five.
Frame # | Time (s) | Distance (cm) |
1 | 0 | |
4 | 3/30 | |
7 | 6/30 | |
10 | 9/30 | |
13 | 12/30 | |
16 | 15/30 | |
19 | 18/30 | |
22 | 21/30 | |
25 | 24/30 | |
28 | 27/30 |
Questions
- What forces are acting on the buggy in this video?
- Draw the free body diagram.
- What does the slope of a position vs. time graph tell you?
- How does the motion of the buggy compare to the slope and the free body diagram?
Lab Follow-Up
Suppose the two buggies were going to race. If they both start at the zero mark, how far ahead will the red one be after 5.0 seconds? After 10.0 seconds?
If the blue buggy starts at the 100.0 cm mark and the red one at the zero, how long will it be before the buggies are at the same point?
PHYSICS by MN Partnership for Collaborative Curriculum is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
