Graph between Applied Force and Friction

Methods of Changing Friction

We can reduce friction

(1) By polishing.

(2) By lubrication.

(3) By proper selection of material.

(4) By streamlining the shape of the body.

(5) By using ball bearing.

Angle of Friction

Angle of friction may be defined as the angle which the resultant of limiting friction and normal reaction makes with the normal reaction.

∴                                         tan𝜃 =μ                            [As we know ]

or          θ = tan^-1(μ)

Angle of Repose

Angle of repose is defined as the angle of the inclined plane with horizontal such that a body placed on it is just begins to slide.

In limiting condition F = mg sin α

and       R = mg cos α

So    

∴       [As we know ]

Thus the coefficient of limiting friction is equal to the tangent of angle of repose.

As well as α = θ i.e. angle of repose = angle of friction.

Work done over a rough inclined surface

If a body of mass m is moved up on a rough inclined plane through distance s, then

Work done = force ´ distance

= ma x s

= mg [sin𝜃  + 𝜇 cos𝜃 ]s

=mg s [sin θ + μ cos θ]