The Physics
An encyclopedia of scientific essays

Coefficients of Friction for Aluminum

search icon

Friction is the force between two surfaces in contact that opposes motion or intended motion. Friction can be found by using

f = µFn

where µ is the coefficient of friction and N is the normal force.

In order to calculate the static coefficient of friction (µs), the angle of an inclined plane was increased gradually until the object first begins to slide downward. At that angle, the weight of the object (Fg) would have succeeded in overcoming the force of static friction (fs). Using trigonometry, it can be shown that

fs = Fg sin θ

until the time when the object begins to slip. Therefore

µsFn = Fg sin θ

The normal force (Fn) that the object exerts on the plane surface is equivalent to the weight of the object perpendicular to the plane …

Fn = Fg cos θ

Substituting into the previous equation will produce a new equation …

µs = tan θ

helpful for determining the coefficient of static friction, with the angle of the inclined plane being an important component.



  1. Setup equipment as shown as in the diagram. (The ramp is covered in aluminum foil)
  2. Place an object of any material (ex. penny = copper) at the top of the board, which is initially level.
  3. Lift board up on one end, pivoting it on the table, until the the object starts slipping.
  4. Determine the parallel component of the acceleration due to gravity using Logger Pro.

LoggerPro determined the acceleration due to gravity parallel to the ramp. Using trigonometry we can determine the angle of inclination …

sin θ = gparallel/g
θ = sin-1 (gparallel/g)

Material gparallel (m/s2) θ (°) µstatic
Plastic 3.67 21.9 0.40
Cardboard 3.9 23.45 0.43
Leather 6.75 43.53 0.95
Copper 4.84 29.59 0.57

Leo Tam, Jenny Hua, Stephanie Ma -- 2005

Students Choice
  1. Electricity & Magnetism
    1. The (dysfunctional) crystal radio
    2. The Kelvin water-drop electrostatic generator
    3. The two-way telegraph
    4. Magnetic field of a MetroCard
  2. Acceleration
    1. Acceleration of an elevator, hydraulic
    2. Acceleration perturbations of daily living
  3. Index of refraction of various household liquids
    1. glycerin, floor cleaner, degreaser, shower gel, baby wash
    2. vinegar, honey, floor cleaner, throat medicine, foot wash
  4. Coefficients of Friction
    1. Coefficients of friction for aluminum
    2. Coefficients of friction for glass
    3. Coefficients of friction for granite
    4. Coefficients of friction for paper
    5. Coefficients of friction for rubber
    6. Coefficients of friction for human skin
    7. Coefficients of friction for steel
    8. Coefficients of friction for wood