PHYSICS
LAB: COEFFICIENT OF FRICTION FOR A TOY CAR ON A HILL
NAME____________________
DATE _________ PERIOD ___
LAB PARTNERS: 1____________ 2____________ 3____________ 4____________ 5____________
PURPOSE: To find the coefficient of sliding friction of the tires of a toy car relative to masonite.
PROCEDURE:
1. Obtain a masonite board with which you can set up an inclined plane for the car to climb.
2. Record a brief description of the car used in the space provided.
3. Determine the mass of the car and record in the space provided.
4. Adjust the angle of the inclined plane so that while attempting to climb the hill, the car will essentially
remain in the same position with its wheels spinning. Record the angle in the space provided.
NOTE: The car may not remain in a stable position; it may veer off to one side or the other. Run a few trials,
and use your best judgment for the angle.
FORCE DIAGRAM:
On the diagram of the vehicle below, draw and label vectors representing the following forces:
F⊥
Fn
Ff
W
FII
The forces should be drawn so that the special relationship between W, FII and F⊥ is evident.
Be sure that Fn, the "normal" force, is drawn so that it unquestionably looks "normal" (perpendicular) to the
incline.
W
θ
DATA/CALCULATIONS/CONCLUSION:
1. Description of car: ________________________________________________
2. Mass of car = ________g = ________kg
3. Angle: ________degrees
4. Weight of car = (m)(g) = ________kg x ________m/s/s = ________N
5. FII = W sin _____ = ________N x ________ = ________N
6. F⊥ = W cos ____ = ________N x ________ = ________N
7. Ff = FII = ________N
8. µk = Ff = ________N =
Fn
N
Fn = F⊥ = ________N
check your work: tan θ = tan ____ =
Coefficient of Friction Lab
Fn = Normal Force
Ff
F
Ff = F
Fn = W
Ff
µ=
Fn
Fn
Ff
FII
W = Weight
θ
θ
F f = F ric tion Fo rc e (N)
F = Applied Force (N)
µ = coeffici en t of fric tion (s tati c o r kineti c)
F⊥
F⊥ = W cos θ
FII = W sin θ
Ff = FII
Fn = F⊥
Ff
µ=
Fn
W
Limiting Angl e of Repos e (Fin ding µ s u sing tan θ )
Record the weight of the box alone as weight as W. Place it on the board with the bottom surface of the block
facing the masonite surface of the board, and slowly raise the board until the block jus t b egins sli ding. Note
the angle. Repeat several times, and record the average angle.
W = _______
FII = W sin _____ =
θ = _ ____ ___
________N x ________
=
________N
F⊥ =
________N x ________
=
________N
W cos ____
Ff = FII =
=
________N
Fn = F⊥ =
µs = Ff = ________N = _______
Fn
________N
tan θ = tan ____ = ______
N
Compare
µs to tan θ ___________________
Limiting Angl e of Kineti c F ric tion (Finding µ k usi ng tan θ)
Repeat the procedure for Limiting angle of repose, except this time keep ta pping th e blo ck G ENTLY
down th e plan e as you rais e th e boa r d. Note the angle at which the block slides down the ramp at
constan t s peed. Repeat several times, and record the average angle.
W = _______
FII = W sin _____ =
________N x ________
=
________N
F⊥ =
________N x ________
=
________N
W cos ____
Ff = FII =
θ = _ ____ ___
=
________N
µk = Ff = ________N = ______
Fn
N
Fn = F⊥ =
________N
tan θ = tan ____ = ______
Compare
µk to tan θ _______________
1. How could you QUICKLY determine the coefficient of STATIC Friction using an incline? Use a
complete sentence and describe the process.
2. How could you QUICKLY determine the coefficient of KINETIC Friction using an incline? Use a
complete sentence and describe the process.