The effectiveness of a wedge in splitting a log depends on a number of factors. These include the shape pf the wedge - particularly the angle of the wedge, the size and strength of the log to be split, and the force that is applied to the wedge to drive it in. The force applied o the wedge in turn will depend on things like the weight of the hammer used for driving the wedge, and the speed with which it strikes the wedge. Other things being equal, a each stroke of heavier hammer will drive the wedge deeper as compared to a lighter hammer. The sped with which the hammer strikes the wedge has no relationship with the weight of hammer. Generally higher the height from which the hammer is brought down to the wedge, greater is the speed at which the hammers strikes the wedge.