<P> where F is the normal force between the load and the plane, directed normal to the surface, and μ is the coefficient of static friction between the two surfaces, which varies with the material . When no input force is applied, if the inclination angle θ of the plane is less than some maximum value φ the component of gravitational force parallel to the plane will be too small to overcome friction, and the load will remain motionless . This angle is called the angle of repose and depends on the composition of the surfaces, but is independent of the load weight . It is shown below that the tangent of the angle of repose φ is equal to μ </P> <Dl> <Dd> φ = tan − 1 ⁡ μ (\ displaystyle \ phi = \ tan ^ (- 1) \ mu \,) </Dd> </Dl> <Dd> φ = tan − 1 ⁡ μ (\ displaystyle \ phi = \ tan ^ (- 1) \ mu \,) </Dd> <P> With friction, there is always some range of input force F for which the load is stationary, neither sliding up or down the plane, whereas with a frictionless inclined plane there is only one particular value of input force for which the load is stationary . </P>

What is the normal relation on the inclined plane