A particle of weight 15N is resting on a plane inclined at an angle of 30°. Find : a) the normal force exerted on the particle, b) the coefficient of friction between the particle and the plane, providing it is in limiting equilibrium

The normal force can be calculated using cos(30)x weight = 12.99N From the equation F=μN, μ can be calculated as F/N and as it is at rest F is equal to component of weight parallel to the plane Therefore, F= sin(30)x15 = 7.5N so μ = 7.5/12.99 = 0.577