figure shows a block kept on a rough inclined plane

A block kept on a rough inclined plane experiences three main forces:

• Gravitational force (mg): Acts vertically downward.
• Normal force (N): Acts perpendicular to the surface of the inclined plane.
• Frictional force (F_f): Acts parallel to the inclined plane, opposing the motion or potential motion of the block.

The frictional force here is static friction if the block is at rest, preventing it from sliding down by balancing the component of gravity along the plane

. When analyzing such a setup, the forces can be resolved along and perpendicular to the inclined plane. The component of gravitational force pulling the block down the slope is mgsin⁡θmg\sin \theta mgsinθ, and the normal force balancing the perpendicular component is mgcos⁡θmg\cos \theta mgcosθ. The block remains at rest as long as the static friction force is equal to or greater than the downhill component of gravity. The maximum static friction force is μsN=μsmgcos⁡θ\mu_s N=\mu_s mg\cos \theta μs​N=μs​mgcosθ, where μs\mu_s μs​ is the coefficient of static friction

. If an external force is applied along the plane, the block will remain stationary up to certain maximum forces uphill and downhill, which can be used to calculate the coefficient of static friction. For example, if the maximum force down the incline before motion is 2 N and the maximum force up the incline before motion is 10 N, the coefficient of static friction can be calculated accordingly

. In summary, the figure of a block on a rough inclined plane typically illustrates these forces and the balance between gravitational pull, normal reaction, and friction that determines whether the block stays at rest or moves