Physics Olympics

Discover physics in action as we explore the pure science at the heart of several of your favourite Olympic sports events.

With the Olympics fast approaching, it’s not just sport lovers who should be getting excited, but physics fans too. Because whether it’s how fast they run, how high they jump or how many records they break, it’s the laws of physics that these athletes will really be testing.

In scientific terms all sports can be boiled down to physics – in particular the interaction of natural forces; indeed, any influence that causes an object to change speed, direction or shape. There are many forces at play in the sporting field, from gravity (so common and influential it is known as a ‘fundamental’ force) to others like friction and resistance, which are explained in Isaac Newton’s three laws of motion.

Of course, the athletes are important too, negotiating these forces through a combination of instinct and muscle memory. Ultimately, it’s up to you whether you admire Usain Bolt for being an amazing athlete or an unsung master of physics!

So how do these invisible forces contribute to the Olympic events we will be watching this summer? We’ve taken a look at the pole vault, swimming, the hammer throw and gymnastics, four very different events all governed by the same fundamental rules.

The pole vault

Understanding the science behind sport is hard enough when it’s just man versus physics; throw another object into the mix and things get even more complicated.

Pole vaulting, for instance, is based on the same principles as high jump: that is, converting linear momentum into vertical lift.

What makes it different and harder to calculate is the pole, a carbon-fibre tube which is designed to first absorb and then increase kinetic energy (KE) as it bends and flexes. Meanwhile, the athlete still needs perfect timing to ensure the run-up, the plant and the final push over the bar conserve as much potential energy (PE) as possible through these key transitions.

It’s a feat that seems more incredible the more you appreciate how many elements have to go just right to achieve the perfect vault – one reason why Sergei Bubka’s world record of 6.14 metres (20.14 feet) has stood since 1994.

Swimming

When you watch someone swimming, it’s easy to think they are dragging themselves through the water. However, on the contrary, they are being pushed.

Newton’s third law states that to every action force there is an equal, but opposite, reaction force, meaning that as the swimmer kicks with their legs or pulls with their arms, force is applied downwards and backwards, prompting a reactive force from the water pushing the body up and forwards.

Hardly surprising then that the swimmer’s top priority is to reduce drag by any means possible – from perfecting dives to developing new suit materials and designs that minimise surface area when in the water.

But that’s not all. The faster an object travels through any element, the greater the resistance it encounters. As water is 773 times as dense, and 100 times more resistant, than air, top swimmers need to work harder than, say, top sprinters. Conversely, because of buoyancy, they are less likely to get injured.

Somersault

Though rarely seen on its own, the somersault lies at the heart of many Olympic gymnastics disciplines. Somersaults are all about maintaining angular momentum (inertia times velocity! while the body is in the air. During the tumble itself, the arms and legs are tucked closely into the body, helping to reduce inertia as it rotates through 360 degrees in either direction. The more height and velocity achieved through each tumble, the more rotations can be completed before gravity has time to pull the athlete back down.

This explains why a single forward or back somersault can be made from a standing start but multiple tumbles, twists and pikes always require a run-up. This increases linear velocity and changes the angle of projection – allowing for several longer, faster and higher tumbles.

The hammer throw

The hammer consists of three separate and independently moving parts: the handle, 1.2-metre (3.9-foot) chain and, for men, 7.3-kilogram (16-pound) ball; the women’s hammer weighs almost half that at four kilograms (8.8 pounds). Each part reacts to the same forces in slightly different ways.

The perfect throw is split into three key phases. The first is the winds, where the athlete swings the hammer around their head to build up circular momentum. The second is the turns, one to four rotations that maximise the hammer’s PE. And finally the release, which is about judging the right time, angle and height to achieve maximum velocity as a measure of the hammer’s kinetic energy.

Additionally, like all throwing and shooting events, wind resistance can play its part. A strong headwind is capable of reducing a throw’s potential length by several centimetres.