Question

define angle of friction? derive the expression for coefficient of static friction.
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Answer 1

Answer:

The coefficient of friction between any two surfaces in contact is defined as the ratio of the force of limiting friction and normal reaction between them. u= F / R. Angle with the resultant of force of limiting friction F and normal reaction R makes with the direction of normal reaction R is angle of reaction

Explanation:

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Answer 2

In the state of limiting friction, the angle which the resultant makes with the normal reaction is called the 'angle of friction'.

• For any two given surfaces, the limiting frictional force is directly proportional to the normal reaction.

        $f_{s} \alpha R$

        $f_{s} = \mu_{s} R$

• Here, $f_{s}$ is the force of static friction or limiting friction, $\mu_{s}$ is the constant of proportionality and R is the normal reaction force.

• The constant of proportionality is called the 'coefficient of static or limiting friction'. It is the ratio of limiting frictional force to the normal reaction.
• The maximum value of static frictional force which comes into play when a body just begins to slide over the surface of another body is called limiting frictional force.
• The angle of friction is given by the formula,

        $tan \theta_{s} = \frac{f_{s}}{R}$

        $tan \theta_{s} = \mu _{s}$

• Here, $\theta_{s}$ is the angle of friction.