PhyFl18-SS2.6.7 Okay, so here is one like THT2B.18. Even though we know it is just the AVERAGE acceleration we can use that area to determine the velocity of the bullet as it moves through the barrel and we can even determine the length of the barrel. It is simply a matter of finding the areas of the lower graphs to determine the function of the graph above. This is the basis of integral calculus.