How is it that when Micheal Phelps swims the butterfly he can glide effortlessly through the water and somehow resembles the mammal for which the stroke is named? Well it may not seem so, but Phelps is a physicist. He has perfected the stokes so that he is working with the laws of physics and mechanics, reducing drag, minimizing his surface area and maximizing his force against the water.

The butterfly is arguably the most difficult swimming stroke. The swimmer throws both arms above his or her head and propells their body with a powerful dolphin kick. The main objective is to produce a lot of proplusive forces and reduce the resisitive forces. To reduce drag swmmiers wear hydrodunamic swimsuits, caps, and they even shave their body hair before big races. Another way swimmers resist drag is the streamline position. In streamline the swimmer's arms are up, their hands clasped tightly around their head, their legs are together and their toes pointed. It looks like this:

This reduces the ammount of surface area on the body and therefor reduces the amount of drag. Swimming under water in streamline position with a dolphin kick is faster than swimming above the water because there is water for the body to push against verses if they were swimming above the water where there would be only ar to puch against. This brings us to the second goal in swimming which includes newton's third law: with every force there is an equal and oposite force. The amount of force the swimmer puts on the water with his or her hand or foot determines how far the stroke will take them. (F=ma). The mass of the person remains constant but when the force against the water increases, their accelleration also increases.

Hand position is also a very important part of an efficient stroke. The ideal hand position is where the resultant of the lift and drag forces is opposite to the desired direction of movement. The swimmer the water backward at this angle, propelling them forward.