# Friction_Lab by stariya

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```									Physics                                       Friction Lab                                         Robertson

Partners :

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Weight :
1. Get a group of four books, a loop of string and a yellow spring scale for this section.
2. Open a book and place a loop of string inside the covers and around all or most of the pages.
Close the book and hold the book up by the loop of string

3. Hang the loop of string on the hook of a spring scale.
4. Read the spring scale and record the weight of each book in the data table provided.

Book            Weight of Book (N)

1

2

3

4

Friction Vs Weight :
You will determine if the weight of an object affects the friction that acts on the object.

5. Using the weights of each book, calculate the weight of books 1 and 2; Books 1,2 and 3; and
books 1,2,3 and 4.

6. Determine the static and kinetic friction of the books using the spring scale. Mr. Robertson will give
you a demonstration on this procedure.

Friction and Weight
Total Weight            Static Friction                Kinetic Friction Force
(Newtons)                (Newtons)                          (Newtons)
Book 1

Book 1 and 2

Book 1,2 and 3

Book 1,2 3,and 4
7. Why is it so important to pull the book with the spring scale parallel to the table ?

8. Why is it necessary when calculating kinetic friction to pull the book at constant speed ?

9. As the weight of the books increases, what happens to the static friction force ? ( The force just needed
to get the books started moving across the table)

10. As the weight of the books increases, what happens to the kinetic friction force ( the force needed to
keep the books moving across the table at a constant speed)

11. On the following free body diagram, label the forces (draw force arrows) acting on the book while it is
moving at a constant speed across the table.

12. What was the variable that YOU changed each time you measured the force of kinetic friction.

This is the independent variable

13. What changed as a result of what YOU changed.

This is the dependant variable

14. Using the computer, plot a graph of the force of kinetic friction versus the total weight of the books.
Remember plot your independent variable on the “x” and the dependant variable on the “y”
What relationship does the trend line on the graph represent ? What does this mean ?
Friction Vs Surface
You will determine if changing the amount of surface area in contact with the table (and keeping the
weight of the object constant) will change the kinetic friction force.

15. With a ruler, measure the length and width of three pieces of pre-cut cardboard. Record the dimensions
on the data table. Then calculate the area of the cardboard multiplying length x width

Friction and Surface Area
Cardboard              Length(cm)              Width(cm)               Area (cm2)           Kinetic Friction
Force (Newtons)

Large piece

Medium piece

Small piece

16. Place a book with the loop of string in it on the large piece of cardboard. (Put the word large up). Hook
the spring scale on the loop of string. Pull the book-cardboard system across the table at a constant
speed. If the book slips off the cardboard, fold over a 6 cm piece of making tape and place it between
the book and the cardboard. Read the force on the spring scale while the book and cardboard are
moving. Again, this is the force you are applying to the system with your hand and it is also the force of
kinetic friction between the cardboard and the table. The net force is zero.
 Pull the system across the table several times to be sure you get the came consistent reading.
Record the force in the Friction and Surface Area data table.

17. Replace the large piece of cardboard with medium and then the small piece and repeat step 2.
18. What variable are you changing in this part of the experiment? Does changing this variable change the
kinetic friction force ?

Friction Vs Type of Surface
In this part of the lab we will see what affect the type of surface area has on friction. Again you will keep the
weight constant. To test this, you will pull the same book across various surfaces to see the effect texture has
on the amount of kinetic friction.

19. List your six surfaces in the data table below.
20. Predict which surface will cause the greatest friction. Rank the surfaces from 1 – 6 with 1 as the lowest
amount of friction and 6 as the highest.

21. Place a book with the loop of string in it on the desk. Hook the spring scale on the llp of string. Pull the
book across the desk at a constant speed. Read the force on the spring scale while the book is moving.
Again, this is the force you are applying to the system with your hand and it is also the force of kinetic
friction between the book and the surface. The net force on the system is zero.

22. After calculating the kinetic friction force determine the actual results of which surface provides the
most friction. Again, Rank the surfaces from 1 – 6 with 1 as the lowest amount of friction and 6 as the
highest.
Friction and Type of Surface
Name of surface                 Prediction       Kinetic Friction Force           Actual Result
1-Low 6 high            (Newtons)                   1-Low 6 high
Desk top

Which of the following has an effect on friction? Cite data and other results to support your answer.
Tested                                              Effect on Friction

Weight

_________ has an affect
(check)

Surface Area

_________ has an affect
(check)

Surface Type

_________ has an affect
(check)

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