Guess what this week's post is about? Physics? Haha no. Running of course, and more specifically in response to the people asking (in a whiny, high-pitched voice), "Does it really matter if shoes weigh an ounce or two less? You can't even notice the difference!" It does matter. And here's why: Let's say you're competing in a mile race (maybe the McMullen Mile?) and you've chosen to wear a new pair of spikes that are about 3.5 ounces lighter than your previous pair of spikes (3.5 oz equals about 100 grams). For this demonstration, you are a really good miler, and your average stride length is about 4 meters, or you take a step every 2 meters. Every step you take, you have to carry your weight-- as well the weight of clothing and shoes-- forward (the bigger you are, the more weight you have to carry, but you can take longer, more powerful strides... but that's not the point of this discussion :strawberry:). So if you step every two meters that is approximately 800 steps per mile. If your shoes are 3.5 oz, or .1 kg, lighter, that's 1 Newton less of Force that you have to exert per step... So if you take 800 steps in a mile, that's 800 Newtons of Force that you don't have to use-- which is a lot! And that's only for a mile. If you were running a marathon instead of a mile, you would save almost 21000 N of Force, or about the force required to hold a two-ton car aloft... So wear lighter shoes!