Download Coefficient of Friction Lab

Coefficient of Friction
Purpose:
Hypothesis:
Materials:
Procedure:
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8)
Name:
You will determine the coefficient of kinetic friction for surfaces and find the coefficient of friction on
an inclined plane.
Which surface will have the smallest and largest coefficient of friction? Order the materials from least
to greatest.
“Friction block,” force spring scale, meter stick, wood, cement, pavement, floor tiles, and desk top.
Part 1
Part 2
Measure the mass of your friction block and record in
1) Place one edge of desk on top of 2 or 3 books. Use sohyour data table.
cah-toa to determine the elevation angle.
2) Pull the friction block down the ramp with constant
Determine how to make a perfectly horizontal pull.
velocity to determine the force applied.
Write this procedure down above your data table.
Set up the apparatus as directed. You will repeat each 3) Repeat, this time moving the block up the ramp.
measurement three times to ensure accuracy.
Pull the friction block across the desk top with constant
velocity to determine the force applied.
Repeat the procedure with the block being pulled across
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the floor tiles.
Move to the loading dock.
Repeat the procedure with the friction block across the
cement and pavement.
Move into the gym. Repeat the measurements for the
wooden floor of the gym.
SAMPLE Data Table:
Block’s mass: ______________kg
Part 1:
μk
Surface
Force (N)
Desk top Pull 1
Pull 2
Pull 3
Floor tile Pull 1
Pull 2
Pull 3
Average μk
Part 2:
Moving
Up Pull 1
Up Pull 2
Up Pull 3
Down Pull 1
Down Pull 2
Down Pull 3
Ramp angle
Force applied (N)
μk
Calculation/Conclusion/Analysis: Answer in complete sentences reflecting the nature of the question; unless it is a math
problem – then you need to show all of your work.
1) Draw a free body diagram of the block being pulled on a flat surface. Label all forces.
2) Draw a free body diagram of the block being pulled on the inclined plane. Label all forces.
3) Calculate the coefficient of kinetic friction between the wood block and each of the surfaces.
4) Use the applied force, the force of gravity parallel to the plane, the force of friction to calculate μk for the desk top
moving up and down the plane in part 2.
5) List the objects in order of increasing coefficient of kinetic friction (smallest to largest) from part 1.
6) If there is a difference in the values for the μk on a flat desk and the μk on the inclined desk, what do you think
accounts for that difference?
7) Which surface surprised you based on your hypothesis?
8) Describe how you would determine the coefficient of static friction between the surfaces.
9) Using the free body diagrams from questions 1 and 2, why is it harder to pull the block up a hill versus pulling the
block down a hill? Be specific; use can use words and numbers here.
10) If you applied a force of 25 N on your block up the inclined plane (yes, use the angle and μk you measured), what would
be the acceleration of the block?
11) If you applied a force of 25 N on your block down the inclined plane (yes, use the angle and μk you measured), what
would be the acceleration of the block?