# Olympic Diving Physics

7 August 2012 by Paige Brown, posted in Uncategorized

In honor of the Olympics, today's post is about the Physics of Diving!

Diving is a beautiful yet beastly hard sport, full of flipping, twisting and lots of guts. Diving is all about form, body lines, and getting into the water without making a splash. Divers flip and twist in a variety of body positions, including the tuck (legs bent and tucked into the chest), pike (legs straight and body bent only at the hips), and straight or layout positions.

Flips, Flips, Flips.

When a diver flips forward off of the diving board, he or she may begin by throwing into a pike position to gain angular speed in a flipping direction while his or her feet remain on the board as long as possible. Almost all of a diver’s “work” is done on the diving board – by putting energy into the board, a diver harness the “equal and opposite” Newton’s Third Law of Motion, with that energy eventually being transferred back into projecting the diver up and forward away from the diving board.

As my own coach used to tell me, the diving board is a diver’s best friend. The diver should not stomp on the board, but rather smoothly ride the board in order to transfer a maximum amount of the energy used to bend the board down toward the water back into propelling a diver into the air. A stomp or loud noise on the board indicates that the diver’s jump has not been properly timed with the movement of the board, and thus some of the movement and energy of the board has been lost before the dive could begin.

The physics of springboard diving is different than the physics of platform diving, but in many ways they are similar. A platform diver must generate upward and forward momentum off the platform by bending the knees (almost like loading a spring) and pushing off the hard platform surface with toes, ankles, knees and hips, while also using arm swings and/or a running approach to generate more height and flip.

Diving is all about lines and form. A dive is judged as much for aesthetics as for technical completion, with pointed toes, straight legs, and clean water entries making for better scores. An excellent diver will make an incredibly hard skill looks easy, with barely a splash on the end.

When diving in the forward direction, a diver uses a series of steps and a “hurdle” on springboard while using a run and “skip” on platform to gain momentum for flipping and twisting motion in the air. This is called the diver’s “approach”. The approaches on springboard and platform look very different – because a springboard is very flexible while the platform is a very hard surface – but they serve the same purpose. By performing a hurdle or skip motion near the end of the board or platform, which typically involves pushing forward and away from oneself down into the board or platform surface while leaning slightly backwards, a diver is converting the forward momentum of their run into upwards and flipping momentum.

By quickly halting the run with a skip and push forward and down into the platform, a diver’s body is suddenly projected up and over into a flip. This is rather simple physics… but makes for impressive results, with divers able to generate up to 4 ½ flips off the platform!

With forward momentum being converted into upwards momentum, a diver uses flexion at the shoulders and hips to throw their bodies into a flipping direction. The diver must do this while his or her feet are still in contact with the board… once in the air with nothing to push off of, the only thing a diver can do is shorten their radius in the flipping direction (brining their arms and legs close to their body in a tuck position for example) to speed up the flip. The stronger the arm throw and hip bend while the feet are still on the board, the more flip a diver can generate.

The Rip Entry

The splashless water entry is the culmination of a perfect dive. In keeping with the aesthetics of the sport, a judge wants to see an entry that slices through the water without a splash. The “rip” entry, so called because the sound of entering the water with no splash literally sounds like the ripping of paper, is achieved when the diver’s hands (which are clasped together in a flat palm-up position) are perfectly perpendicular with the water, and the diver’s entire body down to the tips of the toes go into the same hole as the hands made in the water’s surface. You can think of the water “swallowing” the diver – with the entry a diver wants to pull the water down and around him- or herself. A diver also typically “swims” or spreads his or her arms apart immediately after hitting the water, in order to pull the rest of the diver’s body down into the water.

A rip entry is one of the most peculiar things I have ever felt in my life… if feels like your entire body has slid and disappeared into a tiny and ephemeral hole made by your hands. Once under the water’s surface, all that water that you have pulled down with you almost ‘bubbles’ back up to the surface under you – I used to feel like I would float back to the surface on my own “rip” bubbles!

Sometimes, you may see divers perform their dives into bubbles when training – a big aerator at the bottom of the pool creates bubbles that rises to the water’s surface. These bubbles break the surface of the water so that if the diver lands wrong – in a flat position for example, then the “smack” won’t hurt as badly! It’s almost like using mats or cushions in the water. Fun fact, when diving outside into cold water, the surface of the water feels “harder” due to a higher degree of surface tension, and can be rougher on a diver’s body! By keeping the diving water warm, the surface is a bit more forgiving.

When diving off of 10meter platform, a diver hits the water at nearly 35miles per hour! Now that is an impact! A free-falling diver accelerates at 32 feet per second per second to the water. A platform diver must have very strong shoulders and triceps to sustain the entry and pull through the water at that speed. I used to have to tape my wrists so that the impact of the water wouldn’t force them into a harmful position, and even then, before I was strong enough, the impact would often crash my hands into my head.