Anybody good at physics??

* I suspect there may be other forces at work other than drag. Wave generation is an interesting one and it turns out that being a little bigger might be an advantage. When you swim, you generate a wave. You actually make two waves, a bow wave and a stern wave. For non-planing boats, there's a point at which going faster becomes increasingly difficult due the interaction between these waves. Turns out the point at which things get harder is a function of the length of the waterline where a larger person would be better off. Don't know if this applies to humans swimming but I suspect it would. "Hull length" definitely applies to humans.That is why there are so few short sprinters.This relates to height and not weight so has little applicability to the current discussion.

"Hull length" definitely applies to humans.That is why there are so few short sprinters.This relates to height and not weight so has little applicability to the current discussion. I think it is more a function of waterline... at least that is what we used to use to handicap sailboats. Height will increase your waterline but so will girth.

you still have to accelerate your mass to overcome the drag forces in order to maintain a constant velocity. F=ma does apply here. Exactly. Thus I'm confused why now two people are saying that F=ma does not apply. You must apply force to the water to accelerate your mass. Isn't that F = ma?

Exactly. Thus I'm confused why now two people are saying that F=ma does not apply. You must apply force to the water to accelerate your mass. Isn't that F = ma? In my case there is very little acceleration after the push off, velocity remains more or less constant. So a=0 (in fact, in my case probably a

Exactly. Thus I'm confused why now two people are saying that F=ma does not apply. You must apply force to the water to accelerate your mass. Isn't that F = ma? It applies--it's just that it cancels itself out. If you have more mass, you have to apply additional force to accelerate. But, because of inertia, the additional mass causes you to hold on to that momentum longer. So, THEORETICALLY, the catch and the push-off require additional force, but they should take you further.

Aquatic mammals are generally not lean. I'm not really sure this is 100% relevant. Aquatic mammals need a layer of fat so they can survive in cold water. I guess it does prove that animals can still swim fast even with lots of fat, but seals and whales aren't exactly built like humans, either.

Aquatic mammals are generally not lean.

Here's my pseudo-science contribution to the thread: * Drag forces are not directly related to mass but you still have to accelerate your mass to overcome the drag forces in order to maintain a constant velocity. F=ma does apply here. Being heavier hurts. * While drag forces are not directly related to mass, they are related to cross-section and surface area. If you increase your girth, you increase your drag. * Bouyancy makes a difference. Riding higher reduces the surface area and cross-section exposed to the water. Where you pack on that extra weight has a lot to do with whether or not this really helps. If only we could add fat in full body suit shapes. * Pushing off a wall or starting block requires more force for a heavier person. You are accelerating your mass so there is really no getting past f=ma. Work is force applied over a distance. No need to go into that. * I suspect there may be other forces at work other than drag. Wave generation is an interesting one and it turns out that being a little bigger might be an advantage. When you swim, you generate a wave. You actually make two waves, a bow wave and a stern wave. For non-planing boats, there's a point at which going faster becomes increasingly difficult due the interaction between these waves. Turns out the point at which things get harder is a function of the length of the waterline where a larger person would be better off. Don't know if this applies to humans swimming but I suspect it would. My conclusion: It is hard to tell if packing on a few extra pounds really makes that much difference in swimming. Modeling a rigid body moving through the surface of the water is complicated enough. Accurately modeling a human thrashing about on the surface of the water is not going to happen with our current technology. So, there is not way to do a real objective analysis. We are left with anecdotal evidence like, "I shaved 2 seconds off my 50 free after I lost 10 lbs." Or maybe, "some fat guy blew me away in the 50 free last week. I guess the extra weight doesn't hurt him at all." It definitely isn't the liability it would be in running or cycling.

Even though I completely agree that this is impossible to quantify, I can't resist commenting... I think F=ma is a non-factor in the water. Any of the swim strokes is a cycle of negative and positive acceleration. The negative acceleration comes from drag, which does not strictly depend on mass, although kind of indirectly via body shape like you said. Greater mass is a good thing in the slowing-down phases of the stroke, provided the drag force is constant, because the negative value of acceleration is inversely related to mass. Imagine throwing a ping pong ball versus a golf ball. Which one slows down faster? The flip side of this, of course, is that it's harder to accelerate in the positive acceleration phases of the stroke. But it should be a wash, right? I think you're right, except for the push-off. Even though it takes more effort to push off if you have more mass, pushing off is pretty easy. So the additional "work" would not be any more fatiguing than if you had less mass, but you would generate more momentum. (Not that this comment has anything to do with whether or not or how much weight loss would actually affect swimming speed in real life.)

So a=0 (in fact, in my case probably a