Karthik R
What is required to roll a log is the energy to overcome the rolling resistance, which involves friction energy (caused by slipping of the surface), kinetic energy of the log, and internal energy due to the deformation of the log and the road surface. For dragging a wood cube on the same surface, the energy is consumed by friction energy and the deformation of the wood. The friction between a wood cube and the ground is usually much higher than rolling friction of a wood log, thus it takes more energy to drag a wood cube than roll a wood log.