PHYSICS
LAB: COEFFICIENT OF FRICTION
NAME ___________________________
DATE ________________ PERIOD ____
LAB PARTNERS: 1___________
2_____________ 3_____________ 4____________
PURPOSE: To experimentally determine the coefficients of static (standing) and kinetic (sliding) friction
two different pairs of surfaces.
APPARATUS & EQUATIONS: See separate sheet.
PROCEDURE: See other side.
DATA & RESULTS: See separate sheet.
QUESTIONS/CONCLUSIONS:
1. a) Cite your average experimental values for the coefficients of static and kinetic friction for the cases
below:
masonite/masonite:
µ s = ________
rubber/masonite:
µ s = ________
µ k = ________
b) From reading and class discussion, which coefficient should be larger, static or kinetic?
c) Cite an example from common experience (not in the physics lab) which supports the answer in b).
d) Which pair of surfaces should have the highest coefficient of friction, masonite/masonite or
rubber/masonite?
e) It would be reasonable to expect that µ k for rubber would be < greater than > < less than
µs
for rubber, and
< greater than >
< less than >
µ k for masonite.
3. a) How could you QUICKLY determine the coefficient of STATIC friction using an incline? Briefly desc
the process, not just the last step. USE COMPLETE SENTENCES AND GOOD WRITING TECHNIQUES.
b) How could you QUICKLY determine the coefficient of KINETIC friction using an incline? Briefly
describe the process, not just the last step. USE COMPLETE SENTENCES AND GOOD WRITING
TECHNIQUES.
PHYSICS
LAB: COEFFICIENT OF FRICTION
PROCEDURE:
Coefficient of Static (Standing)Friction
Trial 1. Weigh the block with the spring balance, and record as weight W. Pull the block very
carefully with the spring balance, with the masonite face of the block sliding on the masonite face of
the board, until the block just slips. Note the maximum spring balance reading just before the
block moves. Repeat several times, and record the average spring balance reading as force F.
Trial 2. Put a 10 N weight on the block and record the sum of the previous weight of the block plus
the added 10 N as weight W. Pull on the block as in trial 1, and note the spring balance reading.
Repeat several times, and record the average spring balance reading as force F.
Trial 3. Remove the added 10 N weight, and record the weight of the block alone as weight W. Stand
block on the masonite end, thus reducing the masonite surface area in contact with the board. Pull
on the block as in trials 1 and 2, and note the spring balance reading. Repeat several times and
record the average spring balance reading as force F.
Trial 4. Repeat the procedure in trial 1, except with the rubber face of the block sliding on the
masonite surface of the board.
Coefficient of Kinetic (Sliding) Friction
Trial 5. Record the weight of the block alone as weight W. Pull the block with the spring balance at
constant speed, with the masonite face of the block sliding on the masonite face of the board. Note the
spring balance reading. Repeat several times, and record the average spring balance reading as
force F.
Trial 6. Put a 10 N weight on the block and record the sum of the previous weight of the block plus
the added 10 N as weight W. Pull the block at slow constant speed as in trial 5, and note the spring
balance reading. Repeat several times, and record the average spring balance reading as force F.
Trial 7. Remove the added 10 N weight, and record the weight of the block alone as weight W. Stand
the block on the masonite end, thus reducing the masonite surface area in contact with the board.
Pull the block at constant speed as in trials 5 and 6, and note the spring balance reading. Repeat
several times, and record the average spring balance reading as force F.
Limiting Angle of Repose
Trial 8. Record the weight of the block alone as weight as W. Place it on the board with the masonite
surface of the block facing the masonite surface of the board, and slowly raise the board until the
block just begins sliding. Note the angle. Repeat several times, and record the average angle.
Limiting Angle of Kinetic Friction
Trial 9. Repeat the procedure in trial 8, except this time keep tapping the block GENTLY
down the plane as you raise the board. Note the angle at which the block slides down the ramp
at constant speed. Repeat several times, and record the average angle.
PHYSICS
LAB: COEFFICIENT OF FRICTION
NAME ______________________
DATE _____________ PERIOD ___
Fn
Ff
Fn
F
Ff
Ff = F
W Fn = W
Ff
µ=
Fn
FII
θ
θ
F⊥
F ⊥ = W cos θ
F II = W sin θ
Ff = FII
F n = F⊥
µ=
Ff
Fn
W
DATA & RESULTS
************************************************************
************************************************************
* * * * * *
STATIC FRICTION
Surfaces:
_______________ and _______________
F
W
Ff
Fn
µs
(N)
(N)
(N)
(N)
TRIAL 1: REGULAR
TRIAL 2: ADDED
WEIGHT
TRIAL 3: SMALLER
AREA
AVERAGE
////// ////// ////// //////
/
/
/
/
Surfaces: _______________ and _______________
F
W
Ff
(N)
(N)
(N)
Fn
(N)
µs
TRIAL 4: REGULAR
*********************************************************************
*********************************************************
KINETIC FRICTION
Surfaces: _______________ and _______________
F
W
Ff
Fn
µk
(N)
(N)
(N)
(N)
TRIAL 5: REGULAR
TRIAL 6: ADDED
WEIGHT
TRIAL 7: SMALLER
AREA
AVERAGE
////// ////// ////// //////
/
/
/
/
*********************************************************************
*********************************************************
LIMITING ANGLE OF REPOSE
Surfaces: _______________ and _______________
θ
w
Ff
Fn
µs
Fn
µk
tan θ
TRIAL 8:
LIMITING ANGLE OF KINETIC FRICTION
Surfaces: _______________ and _______________
θ
TRIAL 9:
w
Ff
tan θ