STATIC FRICTION LAB

 

PURPOSE - To determine the coefficient of static friction of various surfaces.

 

HYPOTHESIS - Estimate the coefficient of static friction of the various surfaces

 

EQUIPMENT - Block of wood (brick), friction board with different surfaces, spring scale

PROCEDURE

Part One

1. Determine the mass of the block.

2. Attach the spring scale to the block.

3. Place the block on one of the surfaces.

4. Pull the spring scale until the block just begins to move. Determine the maximum amount of pull that can be used WITHOUT moving the block.

5. Record this value and repeat several times.

6. Complete the same testing procedure for each of the surfaces.


RESULTS

Mass of the block: _______________ Kg

 

Weight of the block: _____________ N

 

PART ONE

                  TRIAL NUMBER  - MAXIMUM PULL  KG

SUR-

FACE TYPE

TEST 1

TEST

 2

TEST

 3

TEST

 4

TEST

 5

AVE

STATIC FORCE   N

BARE WOOD

 

 

 

 

 

 

 

PAINT

 

 

 

 

 

 

 

 

PAPER

 

 

 

 

 

 

 

 

PLASTIC

 

 

 

 

 

 

 

 

 

PART ONE

SURFACE

TYPE

MAX STATIC FORCE   

N

NORMAL FORCE

N

COEFFICIENT OF STATIC FRICTION

MU

m

BARE WOOD

 

 

 

PAINT

 

 

 

 

PAPER

 

 

 

 

PLASTIC

 

 

 

 

 


PART TWO

1. Place the block on one of the surfaces.

2. Raise one end of the board until the block just starts to slide.

3. Measure the height raised.

4. Determine the angle of the incline.

5. Determine the Tangent of the maximum angle of incline.

 

LENGTH OF BOARD __________ M

 

                  TRIAL NUMBER  - MAXIMUM HEIGHT  METERS

SUR-

FACE TYPE

TEST 1

TEST

 2

TEST

 3

TEST

 4

TEST

 5

AVE

HT

M

MAX

ANGLE

BARE WOOD

 

 

 

 

 

 

 

PAINT

 

 

 

 

 

 

 

 

PAPER

 

 

 

 

 

 

 

 

PLASTIC

 

 

 

 

 

 

 

 

 

PART TWO

SURFACE

TYPE

COEFFICIENT OF STATIC FRICTION

MU

m

TANGENT OF THE MAXIMUM ANGLE OF INCLINE

PERCENT DIFFERENCE

BARE WOOD

 

 

 

PAINT

 

 

 

 

PAPER

 

 

 

 

PLASTIC

 

 

 

 

 

 

 

AVERAGE

 


Part Three

Surface Area and Friction

  1. Select the surface showing the best Percent Difference between the coefficient of friction and the tangent.
  2. Use the same brick and board as in part one and two.
  3. Retest the brick in the same orientation as in Part 1.
  4. Place the brick on a side then test for the maximum static force needed to move the brick.
  5. Place the brick on an end then test for the maximum static force needed to move the brick.
  6. Calculate the coefficient of static friction between the surface and the brick.

 

Surface used: ____________________

 

                  TRIAL NUMBER  - MAXIMUM PULL  KG

SUR-

FACE TYPE

TEST 1

TEST

 2

TEST

 3

TEST

 4

TEST

 5

AVE

STATIC FORCE   N

m

Bottom

 

 

 

 

 

 

 

 

 

Side

 

 

 

 

 

 

 

 

 

End

 

 

 

 

 

 

 

 

 

 

Percent Difference between Bottom and Side: ____

 

Percent Difference between Bottom and End: ____

 

% Diff = 100 (Bottom – other) / Bottom


Part Four

Normal Force and the Coefficient of Friction

  1. Select the surface showing the best Percent Difference between the coefficient of friction and the tangent.
  2. Use the same brick and board as in part one and two.
  3. Place the brick on the surface then test for the maximum static force needed to move the brick.
  4. Place one wooden block on top of the brick.
  5. Test for the maximum static force needed to move the brick.
  6. Continue to place wooden blocks on top of the brick until 5 blocks are used OR the spring scale maximum reading has been reached.

 

Surface used: ____________________

 

                  TRIAL NUMBER  - MAXIMUM PULL  KG

 

TEST 1

TEST

 2

TEST

 3

TEST

 4

TEST

 5

AVE

STATIC

FORCE  

N

Brick

 

 

 

 

 

 

 

1 Block

 

 

 

 

 

 

 

2 Block

 

 

 

 

 

 

 

3 Block

 

 

 

 

 

 

 

4 Block

 

 

 

 

 

 

 

5 Block

 

 

 

 

 

 

 

 

 

 

Total Mass

Kg

Normal Force

N

STATIC

FORCE  

N

m

Brick

 

 

 

 

 

1 Block

 

 

 

 

2 Block

 

 

 

 

3 Block

 

 

 

 

4 Block

 

 

 

 

5 Block

 

 

 

 

 


ANALYZED DATA  

PART ONE

A. Complete each data table.  

NOTE - The Weight = m g   Weight = Fn

B. Determine the Coefficient of Static Friction   

mu =  f  /  Fn

C. Determine the percent differences between the estimated and the actual coefficients of static friction.

 

PART TWO

A.          Complete each data table.

B.           Calculate the percent difference

Percent Diff = 100 (Pt 1 – Pt 2) / Pt 1

 

PART THREE

A.          Complete the data table

B.           Find the percent difference between orientations

 

% Diff = 100 (Bottom – other) / Bottom

 

PART FOUR

A.          Complete the data tables.

B.           Make a graph of the number of Normal Force (X-axis) versus the Frictional Force (Y-Axis).

C.          Sketch the graph and determine the slope, y-intercept and correlation coefficient.


 

CONCLUSION

1. What causes static friction?

2. What does the coefficient of static friction actually represent?

3. Rate the surfaces from the smallest to largest coefficient of static friction.

4. Explain how the tangent of the maximum angle attained without sliding compares to the coefficient of static friction.

5. Explain how changing the surface area changes the coefficient of static friction.

6. Explain how changing the normal force changes the coefficient of static friction