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### Friction Lab

Force Friction

Purpose:

In this activity you will be investigating the relationship between the force normal pushing two surfaces together and the force friction that is created as the surfaces move past each other.

Info:

• Above is a picture of the set up of the lab.  Make sure you copy this picture into your lab book and show all the forces acting on the object.

• Make sure your force probe is set on 10 N.

• Do not exceed 1.5 kg in the box.

• Evenly distribute the masses in the box.

• Zero your force probe immediately before each trial.

• When you pull your box across the table make sure you do it at a slow steady speed.

Procedure Part 1:  Virtual

1. Open the program found here.
2. Look at all the different possible surfaces and pick the one that you would like to study.
3. Use the up and down arrows to change the mass of the object on the table.  I would like you to do 10 different masses through the course of this experiment.
4. Set up a data table to track the mass of the object on the table, the force normal (equal to gravity), and the force applied (equal to friction).
5. Hit the start button and watch as the person pulling on the box increases the force applied.  At some point the box should start to move across the table at a slow and steady speed.  Write down what seems to be the average force needed to pull the object at a slow and steady speed.  Using the graph below I would estimate the average applied force needed to move at a slow steady speed at 0.64 N.

7. Repeat this procedure for 9 other masses.
8. Make a graph of force friction vs. force normal and show the graph to your teacher.  If they approve your graph, please put it and the equation for it into your lab book.
9. Give a sentence of conclusion telling what you learned and sources of error.

Procedure Part 2:  Actual

• Hook your force probe to channel 1 of your Lab Quest and then open Logger Pro on your computer.

• Set up a data section of your lab book that looks like this

mass of box = _________________ g

 Mass in Box (g) Force Gravity/Normal (N) Force Applied/Friction (N) Make enough rows for 10 different masses

• Set your force probe horizontally on your lab table and zero the probe by clicking on the "Zero Button" on your Logger Pro tool bar.

• Begin collecting force data to make sure that you zeroed your probe properly.  Slowly pull the box across the lab table at a slow, steady speed.

• Record the average force applied to the box to move it across the lab table at a slow steady pace.

• Repeat this procedure for a total of 10 different masses inside the box.  Remember not to exceed 10 N of force applied and not to exceed 1.5 kg inside the box.

• Create a graph that shows force friction (y) vs. force normal (x).  Make sure both the graph and the equation for the graph make it into your lab book.

Things you need in lab book:

1. Purpose

2. Info including a picture of the lab setup.

3. Two data tables, one for each part.

4. A graph for each part.  Your graph should be Force Friction on the y-axis and Force Normal on the x-axis.

5. An equation relating force friction and force normal.

6. A statement of conclusion and sources of error and ways to correct the errors.