Physics and the racing start.

Not quite. The reduction in velocity is due to the vertical component of the force that the legs provide acting against gravity. You can't consider projectile motion until after you have left the blocks and no other forces are being applied to the swimmer. I'd play with the projectile java applet a little bit. The maximum distance is 45 degrees ONLY when there is no difference between the starting height and ending height. If your starting height is higher than your ending height, the maximum distance will be less than 45 degrees. I can prove this with the equations but playing with the applet would probably be easier to visualize. Also, ballistics makes the assumption that the exit velocity of a gun barrel is the same no matter what the angle. For a relatively small mass accelerated by a relatively large force, this is a valid enough assumption for engineering work. Consider however the case of a canon that fires a cannonball with the force of 1g. If the barrel is pointed straight up, the cannonball will never exit the barrel. If the barrel is pointed horizontally, the cannonball will exit so long as it can overcome the friction forces inside the barrel. Thanks,that makes sense.

Here is a photo of Anthony Erving's start at US trials: www.zimbio.com/.../Anthony Ervin Although he is doing a "horizontal" start you can't get your body into that position just pushing forward at 0 degrees. He must have pushed up at around 25 or 30 degrees.

I had one reaction time in Omaha that was 6.0. Did any officials ask you if you were going to go or not? :bolt:

Did any officials ask you if you were going to go or not? :bolt: LOL! I was obviously :bed:when I posted that. .60

LOL! I was obviously :bed:when I posted that. .60 Nice! 0.60 is better than 6.0 for sure! :) I'm pretty consistent with 0.66-0.70 for my reactions at a few pools I've swam at that actually had the technology to record these times. One good drill :D for speeding up your reaction time is to get a good friend (like Speedo) to stand alongside you while on the blocks with a kickboard...in a baseball stance. At the start signal, your friend swings the kickboard, and you're hopefully out of the way before impact!! :afraid: Doesn't take long to get the picture!! (we did this in college a few times for fun)

First, I think Pete and Allen are over simplifying things. If you are ignoring water induced drag, then you are just discussing jumping. In my most humble opinion of course :angel: I hadn't looked closely enough at Peter's analysis.If it leads to the conclusion that the 0 degree starter goes further in the air it must be flawed. It is possible for a 0 degree starter who creates significantly more force when propelling themselves at 0 degrees compared to 30 degree to go further. I couldn't get Pete's applet to work for me, so I just stole his numbers and plugged them into the projection formulas. Given Pete's numbers, you are correct. a = angle (0 or 30 degrees) v = velocity (3.5, 3.8, 4.55 m/s) t = time g = gravity (9.81 m/s^2) y = vertical distance (or height) x = horizontal distance sin(30) = .5 cos(30) = .866 sin(0) = 0 cos(0) = 1 y = vt sin(a) - .5gt^2 x = vt cos(a) The block is .75m tall, so solve for -.75, or when the swimmer hits the water. 30 degrees @ 3.5m/s solve for t: -4.905t^2 + 1.75t + .75 = 0 t = .608 3.5(.608)(.866) = 1.843m 0 degrees @ 3.8m/s solve for t: -4.905t^2 + 0t + .75 = 0 t = .391 3.8(.391)(1) = 1.4858m 0 degrees @ 4.55m/s t = .391 4.55(.391)(1) = 1.77905m How are you going to calculate the transfer of velocities from air to water given different entry angles?

How are you going to calculate the transfer of velocities from air to water given different entry angles? Don't be silly. It's very easy. You take the coefficient of the horizontal distance and multiple it by the amplitude of how much force is being applied at the moment of inertia.

Okay, I'm sending this to Mythbusters. They already tackled swimming in syrup vs. swimming in water. Woohoo :banana:. After that they can answer the age old question of "how fast can you go in a pool filled with diet coke wearing a tech suit made of mentos.":bolt:

Why jump straight out from the start? you want mostly OUT trajectory with some up It's pretty impossible to "stall out" if you dive slightly more up Wind resistance won't slow you down that much after only 8 to 12 feet I think it's a bad idea to jump "slightly down" water is 800 times thicker than air, it's better to have more air time you want to Enter the water in one hole like you were diving through a ring instead of smacking flat "more effective double-leg kicks are executed before surfacing." = SDKs "When I ask coaches why the start should be straight out instead of angled up I never get an answer other than it has been found to be faster." The truth is vectors and trajectory which could be dectected by a series of pressure plates on a block wired to a computer to determine what great starters actually do durining their starts instead of what they think they do or what coaches say they do or should do. Physics is always right. Sometimes coaches just believe an assumption (about swimming) to be true or better rather than experiement. Have a great set position. Hips high Schoeman says keep your hips high, makes sense because the higher your hips, the higher your center of gravity. Lean slightly back while holding the block (create a plyomentric effect) you'll notice some great starters like cesar cielo, swing their back leg up while still attached to the block which raises their center of gravity the most important variables for 15M speed are: + an explosive start great jump & dive, + a clean entry, (proper angles, an ideal arc, not too deep not too shallow) + a great streamline, + lean mass, (heavier swimmers (but still lean and strong) glide further faster than lighter ones) + fast SDK & flutter, + super break out & + fast swimming I'm NOT sure if jumping straight out is faster, than mostly out with some up I think swimmers can't create as much "UP" force doing a track start as they can with both feet forward. The track start increases stability on the block and decreases "block time" by enough to get to 10 or 15 meters faster. "ït is not a good start if it doesn't give you a red chest" ouch for your chest and time. common sense isn't always sensible What is sensible, is the more starts you do with measurement, testing & feedback, the better and faster you will become. It is a skill you can develop and improve. There are best practices for racing starts. They are based in science and fact. HOW? + Watch video of the greatest starters in the world, + Copy their technique + video your starts and watch them in slow motion, (above the water from the side and underwater from entry to break out) + Time 10 & 15 meter sprints + Get one on one expert instruction Anything you do and measure, improves. The problem is that coaches aren't getting their swimmers to do the right stuff or measuring it accurately or enough. Ande

I didn't want to go there. I think you are missing out on all the fun. Once the swimmer hits the water, he has too much control for a simple model to apply. This could be your life's work! but I'd guess that and empirical approach would be much easier. Agreed. Allen needs to go try different start techniques at stop pestering us with mathematical justifications for one side or the other. When he gets to the 15M mark faster than Fort, he should stick with that approach.