Experimental design and analysis (LAB)
Finding the coefficient of kinetic friction
- Unit 2
- 10 points
- About 27 minutes
You can use a calculator on this question, just like on exam day.
A two-part lab question. First you design an experiment to answer a question: what you change, what you measure, the equipment and how you would analyze the data. Then you get a data table from a similar experiment, choose what to graph (often so the points fall on a straight line), plot it and use the slope, the intercept or the graph's shape to answer a question. On the exam: Question 3 of 4. New for May 2027: the free-response section is 95 minutes, down from 100, for all 4 questions (50% of your score), one of each type in this order. Calculator and equation sheet allowed. The CED suggests 25–30 minutes. This question type started in May 2025, so Physics C: Mechanics free-response questions from 2024 and earlier are built differently.
The question and its sources
Students want to determine the coefficient of kinetic friction between a wooden block and a long horizontal table.
Part A: Available equipment
A wooden block with a hook, a long horizontal table with a light pulley clamped at one edge, light string, a set of slotted masses with a hanger (they can also be stacked on top of the block), a balance, a meterstick, a stopwatch, and a motion detector that records position and velocity against time.
Source: Hypothetical lab setup
Part B: Table 1. Block pulled by a hanging mass, total mass fixed at 1.50 kg (slotted masses moved from the block to the hanger)
| Hanging mass m (kg) | Acceleration a (m/s²) |
|---|---|
| 0.40 | 0.84 |
| 0.50 | 1.61 |
| 0.60 | 2.47 |
| 0.70 | 3.24 |
| 0.80 | 4.10 |
Source: Hypothetical data
Suggested time: 27 minutes
Your answers are saved in this browser as you type.
Part (A(i))
3 pointsUsing only the equipment listed in the setup, describe an experimental procedure you could use to collect data that would allow you to determine . Include what you would measure, what you would vary or keep constant, how you would take each measurement, and one step you would take to reduce experimental uncertainty.
Type math plainly, like x^2, sqrt(x) or (x+1)/(x−1).
0 / 2,500 characters
Part (A(ii))
2 pointsDescribe how you would use your data to determine . Include what you would graph and how you would use the graph.
Type math plainly, like x^2, sqrt(x) or (x+1)/(x−1).
0 / 2,500 characters
Part (B(i))
1 pointAnother group used the method described in the data table, keeping the total mass of the block plus all slotted masses fixed at 1.50 kg. Explain why a graph of acceleration a versus hanging mass m should be linear for this method, and derive what the slope and vertical intercept represent.
Type math plainly, like x^2, sqrt(x) or (x+1)/(x−1).
0 / 2,500 characters
Part (B(ii))
2 pointsPlot acceleration versus hanging mass using the data in Table 1, and draw a best-fit line. You can't draw here, so describe the graph you would draw: what goes on each axis (with units), the scale, the points you would plot, and the best-fit line.
Type math plainly, like x^2, sqrt(x) or (x+1)/(x−1).
0 / 2,500 characters
Part (B(iii))
2 pointsUsing your best-fit line, calculate an experimental value for .
Type math plainly, like x^2, sqrt(x) or (x+1)/(x−1).
0 / 2,500 characters
Checking scoring…
Scoring it yourself shows you the rubric, examples and a model answer. Try writing your answer first.