Part A: Determining the Coefficients of Friction

In the first part of this task, you will perform an experiment to practice measuring the coefficients of friction between various materials.

Materials:

You will need the following materials to complete this task:

• A 1.0 - 1.5 m long board, to slide objects down
• A metre stick, or a tape measure
• Objects that can slide or roll down the board
  • Examples include, but are not limited to: blocks made of different materials, different types of shoes, different types of boxes, cans of different sizes, etc.

Procedure:

1. Set up the board as a ramp. Make sure you have enough space to be able to raise and lower one end of the ramp, and to slide objects down the ramp. For this part of the task, we will only be looking at sliding friction, so make sure your objects are not rolling. Make sure to work safely and use objects that won't damage anything or injure anyone.
2. For static friction: Place one object near the top end of the ramp. Slowly lift the end until the objectjust begins to slide. Right at that spot, hold the ramp still, and use the metre stick or tape measure to measure the rise and the run of the ramp in centimetres.(HINT: See the diagram for the rise and run measurement). Record the rise and the run in a data table.
3. For kinetic friction: Lower the ramp back down and place the same object near the top of the ramp. This time, slowly raise the ramp until the object starts to move, but then adjust the ramp downward again until the object ismoving with constant velocitydown the ramp. This may take a couple of tries to get right -- you don't want the object to stop sliding, but you do want it tostop accelerating. Record the rise and the run of the ramp in a data table.
4. Repeat steps 2 and 3 for three more objects of your choosing, making sure they are sliding, not rolling.

Observations:

It might help to set up a data table like this one to record your measurements:

	Static Friction		Kinetic Friction
Object Tested	Rise (cm)	Run (cm)	Rise (cm)	Run (cm)

Analysis:

The slope of the ramp is the same as the coefficient of friction between the object and the ramp.

For static friction -- the amount of friction the object needed to overcome in order to accelerate -- the coefficient (

) is the slope of the ramp tilted just enough to get the object sliding.

For kinetic friction -- the amount of friction between the object and the ramp when the object is in motion -- the coefficient (

) is the slope of the ramp tilted enough to have the object slide at a constant velocity.

1. Calculate the coefficients of static and kinetic friction for your objects (remember that slope is rise divided by run). You may wish to create a new data table, to record your results.

2 Object Tested	3 Coefficient of 4 Static Friction	5 Coefficient of 6 Kinetic Friction
7	8	9
10	11	12
13	14	15
16	17	18

1. 19
2. Which object had the greatest friction with the board? Whichobjecthad the least friction with the board?
3. Based on the types of material you used, do your answers to question 2 surprise you? Why or why not?