AP Physics C - Unit 2, Kinematics – Name:
Lab 3, Acceleration of a Falling Chain background:
In introductory Physics, we limited ourselves to two types of motion: constant velocity and constant acceleration.
APPC is not so limited. Using the calculus, it is relatively easy to analyze more complicated motion. instructions:
In the diagram below you see a cart track on a lab table with a long bead chain draped over a Smart Pulley. The chain is positioned so it will begin to fall when released.
Part A: Qualitative Analysis
Cart Track
Falling Chain pre-lab
1.
To the left of the diagram, draw a free-body diagram for the portion of the chain hanging over the pulley. To the right of the diagram, draw a free-body diagram for the portion of the chain on the lab track.
2.
Discuss with your neighbor or group how the chain will behave when released. What model or model will describe the motion?
3.
The instructor will demonstrate the apparatus. How did it behave? Is this different or the same as motion we observed previously in this class?
4.
Sketch predicted graphs below.
5.
Discuss with the class what variables the motion will depend on. Your group should pick one variable to test. State your experimental question below:

Quantitative Analysis
Carry out the lab you described in the pre-lab above. In the space below, record the relevant data (best-fits and actual graph sketches may be helpful later). ON ONE GRAPH AXIS, sketch and label all of the velocity time best-fits you obtained. Tip: the chain shouldn’t hit the ground while it is still on the sensor.
Summarize your findings below:

Post-lab discussion
Prepare a whiteboard with your experimental question, a summary of your data, and your conclusion, and be prepared to present it to the class. Turn in this sheet, as a neat, easily understandable record of the experiment. Be prepared to write a complete lab report on this investigation, if the instructor asks for it.

KEY
Part A
Graphs 20 pts 5 pts each for x, v, a vs. t graphs, 5 pts linear fit on the a vs. t graph
Question 3: Evidence for non-uniform acceleration: 5 pts, any one of cubic x vs. t graph, quadratic v vs. t graph, linear a vs. t graph
Question 4: Linear a vs. t graph. Because acceleration is changing at a constant rate; b/c resistive force is proportional to amount of chain on table, grav. force is proportional to amount of chain over the pulley
Part B
Graphs 20 pts again. Should see different graphs as students modify the amount of chain hanging over the pulley, and the angle.
Question 9: Changing the angle produces a more-rapidly increasing function.
Question 10: More chain hanging over the edge produces a greater initial force and the function increases more rapidly.