Design a simple experiment that you could carry out in your home to
i) determine the coefficient of static friction between an object and a surface.
ii) prove that the coefficient of static friction is dependent only on the surfaces in
contact, and is not affected by any change in the mass of your object.
(Hint: You might want to look back at the last couple of Support Questions in this lesson,
to help you.)
a) Describe your plan. It must include a list of materials, a diagram of the set-up, and an
explanation of the steps you would take and the data you would collect. (5 marks)
b) Explain how you would analyze the collected data to determine the coefficient of
static friction and prove that it is unaffected by any change in the mass of your object.
(2 marks)
c) State one possible source of error that you might encounter in this experiment and
state the steps you took to minimize or eliminate this source of error. (1 mark)
a) Plan:
Materials:
- Object with a flat bottom (such as a book or a block)
- Surface with different textures (such as a wooden table, tiled floor, or carpet)
- Weighing scale
- Ruler or measuring tape
- Stopwatch or timer
Diagram: (Note: This is a simple diagram and not to scale)
```
___________
| |
| Object |
|___________|
Surface
```
Steps:
1. Set up the experiment by placing the surface on a flat and level area, such as a table or floor.
2. Measure the dimensions of the object (length, width, and height) using a ruler or measuring tape.
3. Place the object on the surface and adjust its position until it is at rest and not moving.
4. Slowly increase the angle of the surface by lifting one end, while keeping an eye on the object. Stop lifting when the object starts moving or sliding.
5. Measure the angle of the inclined surface using a protractor.
6. Record the mass of the object using a weighing scale.
7. Repeat steps 3 to 6 two more times to get a total of three measurements.
8. Calculate the coefficient of static friction using the formula:
Coefficient of Static Friction (µs) = tan(angle of inclined surface)
b) Data Analysis:
1. After collecting the data, plot a graph with the angle of the inclined surface (x-axis) against the coefficient of static friction (y-axis). Each point on the graph represents one trial of the experiment.
2. The graph should show a linear relationship if the coefficient of static friction is indeed dependent only on the surfaces in contact, and not affected by the mass of the object. If the slope of the graph is consistent, it indicates a constant coefficient of static friction.
c) Possible Source of Error and Steps to Minimize It:
One possible source of error could be the lack of precision in measuring the angle of the inclined surface. To minimize this error, use a protractor with a finer scale or measure the surface's angle using a smartphone app specifically designed for angle measurements.