This Week’s Lab

11/13/13 – 11/15/13

Title

• [Title – you need to come up with one]

• Your name and period

Objective:

• To determine the factors that affect friction.

Pre Lab: (answer in complete sentences)

1. In what ways do you think surface area of an object will be affected by friction? (The difference of a block sliding flat compared to a block sliding on its edge.)

2. Draw a free body diagram of a block being pulled to the right at a constant velocity across a horizontal surface. In relation to the direction of motion, which direction does the force of friction act?

3. Predicted the order from least force needed to greatest force needed to slide the block across the surfaces of the bock and: (- metal ramp, - carpet, - lab bench, - cardboard)

4. What effect do you think mass has to do with friction? (If you add more mass what will happen to the force of friction?)

Materials:

• Wooden block

• Spring scale

• Mass set

• Metal ramp

• Carpet

• Cardboard

• Lab table

Procedures Part 1: Different Surface Areas and Surfaces1. Weigh the block using a spring scale and record the result in Newtons.2. Using a block with a loop on the lab table record how much force is needed to keep the block moving at a constant velocity. 3. Change sides of the block and record the results.4. Repeat steps 2 and 3 but use the carpet, back of metal ramp, and cardboard instead of the lab table.

Procedures Part 2: Different Surface Areas and Masses 1. Now add 0.100 kg mass to the block

and record how much force is needed to keep the block in motion on the lab table while it is lying flat.

2. Add 0.100 kg more to the block and repeat until there is 1.000 kg on the block.

3. Repeat steps 1 and 2 but have the block sliding on its side.

Data: Part 1: Different Surfaces

Surface Force - Lying Flat (N) Force - On Its Side (N)

Lab Bench    

Carpet    

Metal Ramp    

Cardboard    

Weight of the block (for both parts):

Part I: Surface Area Data

Data: Part 2: Increasing MassAdded Mass Force - Lying Flat (N) Force - On Its Side (N)

(Mass of Block)    

+ 0.100 kg    

+ 0.200 kg    

+ 0.300 kg    

+ 0.400 kg    

+ 0.500 kg    

+ 0.600 kg    

+ 0.700 kg    

+ 0.800 kg    

+ 0.900 kg    

+ 1.000 kg    

Data Collecting

Record to the nearest 0.25 N!

(2-3 sig. figs.)

Free Body Diagram

Calculations and Graph: (Using T-Charts)

1. Calculate the mass of the block.

2. Calculate the coefficient of friction for each of the trials in PART I (4 calculation total) when the block was lying flat.

3. Make a graph of Mass (x – axis) vs. Force (both lying flat AND on its side on the same graph) (y – axis) from part II

*** Use a Best Fit Curve ***

*** Include a title and units ***

Conclusion: (Answer in paragraph form.)• Identify all variables in the lab as independent,

dependent or controlled. (for parts 1 and 2)• How does friction depend on surface area? Explain

by providing specific examples from your data. • How does this compare to your prediction from the

pre-lab (pre-lab #1)?• List the order from smallest coefficient of friction to

the largest coefficient of friction for each of the surfaces. (- metal ramp, - carpet, - lab bench, - cardboard)

• How does the list compare to your prediction from the pre-lab (pre-lab#3)?

• How does increasing mass affect the force of friction? Explain by providing specific examples from your data. How does this compare this to your prediction (pre-lab #4)?

• Explain in a brief (5 sentences) paragraph what your graph means.

Reminder:

• The lab should be left in the same condition that you found it