A block of mass m m\,m is held in equilibrium on a rough plane inclined at an angle θ \theta\,θ to the horizontal. A horizontal force of magnitude P P\,P acts on the block, pushing it towards the incline as shown in the diagram below.
By resolving the forces perpendicular to the inclined plane, which of the following is the correct expression for the magnitude of the normal reaction force RRR?
R=mgsinθ+PcosθR = mg \sin\theta + P \cos\thetaR=mgsinθ+Pcosθ
R=mgcosθ−PsinθR = mg \cos\theta - P \sin\thetaR=mgcosθ−Psinθ
R=mgcosθ+PsinθR = mg \cos\theta + P \sin\thetaR=mgcosθ+Psinθ
R=mgcosθR = mg \cos\thetaR=mgcosθ