Grade 11 Physics Practice Exam

Work is the transfer of energy due to a force moving a body through a displacement. It is given by the dot product W = F · d = F d cos(theta). When the force is in the same direction as the displacement, theta is 0 degrees and cos(0) = 1, so W = F d which is positive. This means the force adds energy to the object (the object's kinetic energy increases). If the force pointed opposite to the motion, the work would be negative, taking energy away, and if the force acted perpendicular to the displacement, no work would be done by that force (W = 0). Therefore, with the force in the same direction as the displacement, the work is positive.