Question

A body is sliding down an inclined plane (fixed plane ) under its own weight at constant speed.If the inclination of the plane to the horizontal is ${30}^o$. the angle of friction is

• A. ${30}^o$
• B. ${60}^o$
• C. ${45}^o$
• D. ${15}^o$

Answer 1

The correct option is A ${30}^o$

Given,

Speed is constant

Angle of inclined plane is ${30}^o$

Speed is constant means acceleration is zero

Friction force = component of gravitation force.

$\mu mg\cos \theta =mg\sin \theta$

$\mu =\tan {30}^o$

Friction angle is ${30}^o$