Olympic swimmers don’t just dive into the pool like the rest of us. They start on a block called, appropriately enough, a starting block. London will see the Olympic debut of a track-style starting block with an inclined surface and a lip at the back.
The blocks, first used in international competition at the Swimming World Cup in 2009, let swimmers push off from a crouch with the rear leg at a 90-degree angle, optimizing the power of their launch. The block also can detect false starts.
Why does that even matter to a physicist? Because it’s all about acceleration.
Let me start with a simplified case of a swimmer on a flat block, even if the old-style blocks weren’t exactly flat. If the swimmer wants to dive off, he must push on the block to accelerate into a dive. Here is a diagram showing the swimmer and the forces on the swimmer during a start: