Timely Physics

An interesting relationship between the coefficient of kinetic friction $\mu_k$ between a wood block and an inclined surface and the angle of incline when the block travels at a constant speed down the incline. The key requirement for this scenario is to have the block travel at a constant speed down the incline, which means that the acceleration is equal to zero . If the acceleration is zero, that means the net force  $F_{net} = ma$ is also zero. So, we can draw out the forces with a free-body diagram as in the diagram below: We have three forces acting on the block as it slides down the incline: $F_g$, the force of gravity which pulls the block toward the Earth (or ground); $F_N$, the normal force which acts on the block perpendicular to the incline; and $F_{fr}$, the force of kinetic friction which acts opposite the block's direction of motion. Since the net force on the block is zero, the force of gravity parallel to the incline must equal the force of friction and the f...