The angle between the resultant reaction and normal to the plane on which the motion of body is impending is known as-

Explanation

Concept: The angle of limiting friction: Limiting Angle of Friction is defined as the angle which the resultant reaction (R) makes with the normal reaction (R N). In the limiting case, when the body just begins to move, it is in equilibrium under the action of the following three forces: 1. Weight of the body (W), 2. Applied horizontal force (P), and 3. Reaction (R) between the body A and the plane B. The reaction R must, therefore, be equal and opposite to the resultant of W and P and will be inclined at an angle (ϕ) to the normal reaction (R N). This angle ϕ is called the limiting angle of friction or simply angle of friction . Important Points Angle of Repose (α) The angle of repose or angle of sliding α is defined as the minimum angle of inclination of a plane with the horizontal such that a body placed on the plane just begins to slide down. ϕ = tan ​ = −1 ( RN F ) tan μ −1 ( ) Angle of Friction (θ) The angle of friction between any two surfaces in contact is defined as the angle which the resultant of the force of limiting friction F lim and normal reaction N makes with the direction of normal reaction N.