WAEC Physics 2014 Paper

Concept:The weight acts vertically downward, and on an inclined plane it splits into two perpendicular components: one parallel and one perpendicular to the plane.Explanation:The block of mass $M$ has weight $W = Mg$, acting vertically downward.Let the plane be inclined at angle $\theta$ to the horizontal.The component of the weight along the direction of the plane is obtained by resolving $W$ parallel to the plane.This parallel component is $W \sin\theta$.Substitute $W = Mg$ to get the required component as $Mg\sin\theta$.The perpendicular component is $Mg\cos\theta$, which does not affect motion along the plane.Hence, the component parallel to the inclined plane is $Mg\sin\theta$.Answer:A. $Mg\sin\theta$