3.3 - Friction Lab

1. Read and annotate:

   1. objective

   2. theoretical background.

2. Fill in step 1, 2, and 4

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​Do Now

Lesson 3.3 - Friction Lab

Objective: Design and perform an experiment to test the effect of the material of the sliding surface on the force of friction.

Logistics

• Your table group is your lab group

• You can have 3 to 4 members per group.

• Each member must have one of the following roles(description in the role card):

  • Co-ordinator

  • Materials manager (Only send your materials manager to collect materials)

  • Recorder

  • Reporter (Only send your reporter to ask clarifying questions)

​Lab overview

1. The final goal of this experiment is to find out the coefficient of friction between the given weight and the given surface.

2. There will be 4 different surfaces provided:

   1. Paper towel

   2. Foam pad

   3. Wood

   4. Counter top

3. Each lab group will be assigned only one surface and will be asked to find either static OR kinetic friction coefficient

Materials

1. Metal Washer,

2. Meter Stick,

3. Wooden table surface/countertop/ Paper Towel/foam top,

4. string,

5. Newton Spring Scale           

​Step 1: Ask a question

What is the effect of surface material on the force of friction?

​Step 2: Form a hypothesis

The ___________ surface has the highest static as well as kinetic friction.

​Step 4: variables and constants

• ​Independent variable: Surface type

• Dependent variable: Friction force

• Constants: string length, measuring instruments, mass

Categorize

Options (8)

$$+\left(m\cdot9.8\right)N$$  

$$F_{grav}$$  

$$F_{Norm}$$  

$$-\left(m\cdot9.8\right)N$$  

$$F_{frict}$$  

$$F_{app}$$  

$$\mu\cdot m\cdot g$$  

Measuring the external pulling force

Organize these options into the right categories

Vertically balanced forces

Horizontally balanced forces

Reorder

Order the following as the procedure of the experiment

• Measure the provided weight in Newtons using the spring scale

• Hook the spring balance to the provided weight

• Pull the weight parallel to the surface so that it moves at a constant speed (for Kinetic friction)/ just begins to move(for static friction)

• Note down this force as the friction force from the spring scale reading.

• Calculate the coefficient of friction using the formula : (coefficient of friction = Friction force/Normal force)

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2

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5

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• 2
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• 5

• Follow the 'Lab instruction handout' to complete your experiment and data collection.

• Please do not leave your spot and your group, if you have any questions, raise your hand and I will help you.

• Use the equipment gently and only for the purpose of this experiment.

Begin the experiment and data collection

**​Important: Cross out steel if you are not given a steel weight, write cardboard instead.

​Answer the follow-up questions in your lab worksheet.

1. In which trial did the object have the lowest force of friction? Use evidence from the lab to justify your answer. 

2. What is the relationship between friction force and applied force in your lab? Explain your answer using your knowledge of net force and equilibrium.

3. Draw a free-body diagram for the washers when you started applying force but the washers didn’t start moving yet. ( Label your FBD but the exact numbers for applied force and friction force are not needed)

4. Draw a free-body diagram for the washers when they started to move with constant velocity (one FBD for each type of surface. (Label your FBD using the correct forces from the experiment)

​Exit ticket - Friction Lab