SLIDING FRICTION LAB REGULAR PHYSICS PURPOSE - TO CALCULATE THE COEFFICIENT OF STATIC FRICTION BETWEEN TWO SURFACES ESTIMATE OF THE COEFFICIENT OF SLIDING FRICTION ______ To be signed off before starting the lab.

Part One

1. Put a bumper at one end of the air track. 2. Put a flag atop the air cart. 3. Tape a piece of paper at the end of the air track. 4. Place the photogate and accessory photogate at least .800 meters apart. Make sure the air cart passes through both photogates before touching the paper. 5. Launch the air cart by pulling it against the rubber bumper then releasing it. 6. Record the time on the photogate and the distance traveled on the paper.

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Results

Part One Mass of air cart

________ Kg

Distance between photogates ________ m Trial

Time Spee (sec) d (m/s)

Paper Distanc e (m)

1 2 3 4 5 6 7 8 9 10 AVG

2

Acc

m/s 2

Frictio n Force (N)

Coeff Of Frictio n

Part Two

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EQUIPMENT - AIR CART, AIR TRACK, PULLEY, PHOTOGATE AND ACCESSORY PHOTOGATE, STRING, PAPER CLIP, TAPE, PIECE OF SCRATCH PAPER, METER STICK PROCEDURE 1. SET UP THE EQUIPMENT AS SHOWN IN THE DIAGRAM. 2. TAPE A PIECE OF SCRATCH PAPER ON THE END OF THE AIR TRACK NEAR THE PULLEY. MAKE SURE THE TAPE IS AS SMOOTH AS POSSIBLE. 3. PLACE ONE PHOTOGATE SO THE END OF THE CART IS JUST TOUCHING THE PAPER AT FLAG TRIGGERS THE PHOTOGATE. 4. PLACE THE OTHER PHOTOGATE AT LEAST .800 METERS AWAY FROM THE OTHER PHOTOGATE. 5. THE PHOTOGATE SHOULD BE SET ON PULSE WITH THE TIMER ON THE 0.1 mS SETTING (USED TO FIND THE FINAL VELOCITY). 6. DETERMINE THE MASS OF THE AIR CART, FLAG, STRING, PAPER CLIP AND 40 GRAMS OF MASSES (THE SYSTEM MASS). 7. DETERMINE THE MASS OF THE AIR CAR AND FLAG (USE TO FIND THE NORMAL FORCE). 8. PLACE THE 40 GRAMS ON THE HANGER TO ACCELERATE THE AIR CART FORWARD (THE ACCELERATING FORCE).

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RESULTS

DISTANCE BETWEEN PHOTOGATES __________ m SYSTEM MASS ______________ kg ACCELERATING FORCE ____________ N AIR CART AND FLAG MASS ________ kg Without the mass hanging over the edge NORMAL FORCE OF AIR CART AND FLAG ____ N

TABLE ONE TRIAL NUMBER

TESTING INFORMATION PULSE TIME SECONDS

1 2 3 4 5 6 7 8 9 10 AVE 5

STOPPING DISTANCE METERS

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Table Two Calculated Motion Information TRIAL NUMBER

PULSE TIME

SYSTEM ACC

SECONDS

M/S 2

1 2 3 4 5 6 7 8 9 10 AVE

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FINAL VEL NO Friction M/S

STOP DIST. METERS

ACC DUE TO FRICTION M/S 2

Analyzed Results While on the air track (NO FRICTION) A. Make a Free Body Diagram of the air cart while on the air track (no friction). HINT - There are 3 forces. B. Write the long form of the equation for Newton's Second Law under the Free Body Diagram. C. Describe what is causing each labeled force in a short sentence under the equation. D. Determine the theoretical Net Force (both direction and magnitude) E. Use the photogate times to determine the system acceleration of the system while on the air track (no friction) Average CALCULATED SYSTEM ACCELERATION ____ m/s While on air track - No friction

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F. Use the calculated acceleration to determine the final velocity of the air cart just as it reached the paper. Final Velocity on air track ___________ m/s

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While on the paper

G. Determine the final velocity of the system on the paper. Final Velocity on paper ___________ m/s H. Use the stopping distance to determine the system acceleration of the system while on the paper (friction) Average CALCULATED

2 SYSTEM ACCELERATION ____ m/s While on paper - sliding friction occurs I. Make a free body diagram of the air cart while on the paper (sliding friction) HINT - There are 4 (FOUR) forces. J. Write the long form of the equation for Newton's Second Law under the Free Body Diagram. K. Describe what is causing each labeled force in a short sentence under the equation. L. Determine the theoretical Net Force (both direction and magnitude) HINT - Use the Calculated Acceleration M. Determine the TENSION in the string (Average it out to the WEIGHT of the mass - this is only a rough approximation) Tension (forward force) ___________ N N. Determine the frictional force ____________ N (force back)

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TABLE THREE DETERMINING THE COEFFICIENT OF SLIDING FRICTION AVERAGE ACCELERATION ON PAPER M/S 2 SYSTEM MASS KG CALCULATED NET FORCE NEWTONS CALCULATED TENSION NEWTONS CALCULATED SLIDING FRICTION FORCE NEWTONS CALCULATED COEFFICIENT OF SLIDING FRICTION

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CONCLUSION

1. WHAT IS THE DEFINITION OF SLIDING FRICTION? 2. WHAT IS THE DIFFERENCE BETWEEN SLIDING AND STATIC FRICTION? 3. EXPLAIN HOW THE NORMAL FORCE AND WEIGHT OF AN OBJECT ARE RELATED. 4. EXPLAIN WHAT HAD TO BE CALCULATED TO BE ABLE TO DETERMINE THE COEFFICIENT OF SLIDING FRICTION IN THIS LAB? 5. WHAT WAS THE COEFFICIENT OF SLIDING FRICTION BETWEEN THE AIR CART AND THE PAPER IN PART ONE? 6. WHAT WAS THE COEFFICIENT OF SLIDING FRICTION BETWEEN THE AIR CART AND THE PAPER IN PART TWO? 7. WHAT MIGHT HAVE CAUSED ANY DIFFERENCES BETWEEN THE COEFFICIENTS?

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