Similarly, the faster it can be thrown, the more force it delivers. To get more force, one must use a heavier stone or throw the stone faster. The stone's shape and density are also an important function of its effectiveness as a weapon. All else being equal, a large, lightweight rock is a less effective weapon than a small dense one. These days we recognise that lead makes better projectiles than, say, copper or iron and also that small hard projectiles penetrate better than large soft ones.
Forces acting over large areas are less effective than when over smaller ones.
The applied force divided by the area over which it acts is the pressure. If the stone is somehow fashioned to have a pointed end and this strikes the target first, the applied pressure will be much greater for the same force. This is what enables penetration. The cutting effect of a sharp flake of stone similarly enables a relatively small force to exert great pressure at the cutting edge and thereby slice through skin, flesh and sinews. The penetrating power of pointed weapons like the arrow, the spear, the carnivore tooth or the scorpion's sting has been understood for a very long time indeed.