Friction Block Project Instructions (pdf or google doc) and Questions (pdf or google doc)
Purpose: To see how different surfaces affect the coefficient of Friction “m” and the Force of Friction.
Block Materials: You will be given one wood block and you must come up with the rest of the materials to cover 5 of the 6 sides. The sixth side can be plain wood. The surfaces must be fully attached without anything blocking the surface. The surface cannot extend past the block; this insures that the surface area for each side is the same.
Pre-Test Questions: Answer in your notebook before the block is tested.
Why did you choose each of the five materials that you did?
Which side (material) do you think will have the lowest coefficient of friction and why?
Which side (material) do you think will have the highest coefficient of friction and why?
If you pull the block at a constant velocity explain why you can determine μ for each of the surfaces tested by using this formula:μ = FA/Ff.
Testing Materials: String, 500 g mas, Smooth surface or board, Spring scale(s)
Testing Procedure:
Copy this table into your notebook:
Using the electronic scale, find the mass of your block and write it in the table.
Add 500 g (the size of the brass mass) to your block’s mass and write it in the next column.
Convert this new total mass to kilograms and write it in the next column.
Multiple it by the acceleration due to gravity (use -9.8 m/s2) and write the Force of Gravity in the next column.
Since your block is at rest on a level surface, the Normal Force of the surface pushing back up on the block will be equal but opposite to the block and weight’s Force of Gravity. Fill in this last column.
Copy this data table into your notebook and fill in each of your surfaces:
Place the 500 g brass mass on top of your friction block on a level surface.
Wrap the string around your block to pull it and attach the spring scale to the other loop.
Pull your block at a constant velocity. You’ll know it’s a constant velocity if the force remains constant (the scale doesn’t change) as your pulling it.
Record this force under “Applied Force” in the table below.
Turn your block so that a different surface is on the bottom and repeat steps #10-12; don’t forget to write down the surface that is on the bottom of the block.
Repeat for the five other surfaces.
Using the data from the table, determine μ for each of the surfaces tested by using the formula μ = FA/Ff and enter it into the table.
Post-Test Analysis: Answer in your notebook after you have tested your block.
1. Rank your surfaces from the highest coefficient of friction to the smallest.
2. What other surface would you have liked to test that you did not? Why?
3. What were three possible sources of error? How can you prevent them next time?
4. If this were a fellow student’s data, which measurement on which trial was incorrect? How so?