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How to Calculate the Break-Away Friction Contact Area

The break away friction contact area is the point at which an object begins to move as it breaks away from its position on an inclined plane. This is referred to as maximum frictional force and is calculated by solving an equation using coefficient of friction and normal reaction force. To do this you will require the angle for the inclined plane as this is used to calculate the frictional force.

Things You'll Need

6-inch by 12-inch piece of wood
1 penny
Protractor

Instructions

- 1
  Write out the equation used to calculate the maximum frictional force. This is expressed as ̶0;F = mR.̶1;
- 2
  Place the brick near one edge of the piece of wood. Lift the side of the plywood with the brick upwards to create an angle. Continue to lift the side of the wood until the penny begins to move.
- 3
  Measure the angle of the plywood with the protractor. Make a note of the angle on the paper such as 40 degrees.
- 4
  Write out the equation for resolving up the inclined plane. This is expressed as ̶0;F ̵1; 2.5g(sin(40)) = 0.̶1;
- 5
  Write out the equation for resolving perpendicular to the inclined plane. This is expressed as ̶0;R = 2.5(cos(40)).̶1;
- 6
  Input ̶0;sin(40)̶1; and ̶0;cos(40)̶1; into the equation for the coefficient of friction. This equation is expressed as ̶0;sin(40)/cos(40).̶1; Solving the equation results in a coefficient of equilibrium of 0.842.
- 7
  Multiply 0.842 by cos(40) to determine the maximum friction force. The maximum friction force will be 0.64.

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