Lab: Graphical Analysis of Motion
Purpose:
- To review and reinforce the use of graphs for interpreting and visualizing motion
- To review and reinforce the connections between the position (displacement) – time, velocity – time, and the acceleration – time graphs for different scenarios.
Materials Needed:
- Vernier Dynamics Track
- Small ring stand
- Rod clamp
- End stop
- Motion Detector Clamp
- Green Collision cart
- Vernier LabQuest
- Motion Detector
- Laptop computer
- USB cable
Note: ALL questions and drawings must be completed in your Journal under the title “Motion Graphing”. They must be labeled properly, drawn neatly, and answered thoroughly, as you will NOT be printing out the original graphs. Please re-write the question before answering/sketching anything.
Pre-lab set-up:
- Plug in the Vernier LabQuest and attach the motion detector’s cord to both the motion detector (if it’s not already) and “Dig 1” of the LabQuest.
- IF the motion detector is also periodically “clicking” at you, then you know it is working and you’re ready to proceed.
- Position the motion detector’s sensor face so that it is directed down the slope of the track.
- Open the Logger Pro program on your laptop and connect the LabQuest to the computer using the USB cable provided.
- IF the green arrow (“collect” button) is showing in the top right corner of the LabQuest screen, then you are connected properly.
- Hold the cart near the top of your track, and SLOWLY move the cart down the length of the track. As you do this, watch the reading of the motion detector. If the reading ever jumps (i.e. it’s 0.35 m from the top, and the detector shows 1.85 m on the screen), then you know it’s not reading the cart. Adjust the sensor slightly until you never get the “jumps” in the readings throughout the length of the track. If it continues to “jump”, try taping a small notecard on the end of the cart to increase the face that the detector is “seeing”.
Part 1—getting to know your equipment J
1. Hold the cart close to the top of the ramp. Start collecting data: hold the cart at rest for 2.0 seconds, then slowly move the cart at a steady velocity to the bottom of the ramp.
- Draw: the resulting position-time graph and the velocity-time graph.
- Answer: When the cart was slowly being moved down the ramp, was its velocity in the positive direction or negative direction? How do you know?
2. Hold the cart at the bottom of the ramp. Start collecting data: hold the cart at rest for 2.0 seconds, then slowly move the cart at a steady velocity to the top of the ramp.
- Draw: the resulting position-time graph and the velocity-time graph.
- Compare/contrast these graphs (position and velocity graphs) to the ones created in #1)
3. Hold the cart at the top of the ramp, start collecting data, then release the cart. Catch the cart at the bottom of the track. Zoom in on the section of the graph where the cart was freely rolling down the ramp.
- Describe what was happening to the cart during the time you collected data.
- Draw both graphs. Are these both what you would have expected, based on the motion of the cart? Explain how the graphs either do or do not agree with what you expected.
4. Sketch a prediction of the graphs that you would see if you start collecting data, give the cart a quick shove to move it up the ramp, then let it roll back down. (make sure it rolls to no closer than 10 cm from the motion detector at the top of the ramp)
- Now actually collect the data. Answer: Does the resulting set of graphs match your prediction? Sketch the graphs and label each with descriptors of the motion of the cart.
Part 2: Graph Matching—Position-Time Graphs
Expand the position-time graph so that it fills the screen. (just “hide” the velocity-time graph behind the position-time graph)
The button just to the left of the green “collect” arrow is the “generate graph match” tool. Click once on that, and you should see a line on the position-time graph.
When you get the graph to match, your task is to re-create the pattern (line) shown on the graph by moving the cart up and down the track. Please note that you may not be able to do it exactly because of the length of our tracks. If you can’t match exactly, please do the best you can with the shape.
For each of 4 (five) different graphs, do the following in your Journal:
a. Sketch the pattern you are trying to match.
b. Describe, specifically, the motion the car needed to take in order to match the graph
c. Predict the velocity time graph for that motion (sketch it). Peek at the velocity-time graph that you’ve hidden. Does the actual graph agree with your prediction? If not, draw the correct pattern.
Part 3: Graph Matching—Velocity-Time graphs
Expand the velocity-time graph so that it fills the screen. (just “hide” the position-time graph behind the velocity-time graph). Also, add an acceleration-time graph that you will also “hide”.
For each of 4 (five) different graphs, do the following in your Journal:
a. Sketch the pattern you are trying to match.
b. Describe, specifically, the motion the car needed to take in order to match the graph
c. Predict the position-time graph for that motion (sketch it). Peek at the position-time graph that you’ve hidden. Does the actual graph agree with your prediction? If not, draw the correct pattern.
d. Predict the acceleration-time graph for that motion (sketch it). Peek at the acceleration-time graph that you’ve hidden. Does the actual graph agree with your prediction? If not, draw the correct pattern.