The science of Sumo wrestling!

Have a look at the sumo wrestling video clip below, what do you see?

Hakuho vs Harumafuji Day 15 Sumo Natsu Basho May 2014 from Araibira Sumo Coverage on Vimeo.

Two huge guys trying to push each other to the floor or out of the ring. That’s how you win in sumo. Whether they know it or not, every movement they make is dictated by the science of our physical world. After sizing each other up and looking for the best place to grab their opponent, the wrestlers grab hold and try to push each other out of the ring or onto the floor.

Moments of force

They both seek to use the leverage of their arms and legs to apply a force to their opponent and turn them one way or another. This turning effect of a force is also known as the moment of a force. Moments are measured in newton meters (Nm) and can be applied in either a clockwise or anticlockwise direction. When the wrestlers push at each other in the ring and don’t move up or down or backward or forwards, we can say they are balanced with clockwise moments equaling anticlockwise moments.

Centre of Mass

Great! But how can you as a sumo wrestler try to defend yourself against such moments of force? By being as stable as you possibly can be, by using your centre of mass. Centre of mass (sometimes called your balance point) is where most of the mass of a body is concentrated. For a sumo wrestler thats really low down on their body, especially when they crouch down with their thighs and bottoms and huge tummies almost touching the floor.

Moment of Inertia

By taking this type of stance they have made their moment of inertia (which is a measurement of the difficulty in changing the speed and direction of an object) as large as they possibly canOnly when one of the wrestlers manages to use some wrestling skill and application of forces to get their opponents centre of mass moving. so that the opponents centre of mass travels outside his base will he be able to make his opponent topple and win the match.

A demonstration to try out on your teacher!

Ask your teacher to look up at the ceiling and try and balance an upright wine cork on the end of their nose (its very hard to do!).
Now take the cork and push two metal forks into the cork just above its base (as in the image below), try not to jab yourself or anybody else with the forks when you are doing this! Now ask your teacher to try again with the modified cork,and don’t forget to give them a huge round of applause when it works this time!

 

Cork and forks- science made simple CC-BY-NC

corky fork
Photo: science made simple (CC-BY-NC)

 

 

When you attached the forks to the cork you lowered the centre of mass of the whole object, so it became much more stable!

Curriculum Links

England

Key Stage 3 Physics

Motion and forces

using force arrows in diagrams, adding forces in 1 dimension, balanced and unbalanced forces

moment as the turning effect of a force

Balanced forces

opposing forces and equilibrium: weight held by stretched spring or supported on a compressed surface

Wales

Key Stage 3: How things work

the forces in devices and their relationship to work done and power

Northern Ireland

Key Stage 3: Forces and energy

Forces and energy transfer

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Posted in Physics