# Centre of pressure

1. Jul 23, 2012

### marellasunny

Is centre of pressure the same way they represent curl in mathematics ? i.e representation of pressure condensed to a single point?

Also,on a tv show,the presenter said this about the air-brakes on a P-28 fighter,"The air-brakes change the centre of pressure thereby allowing the wind-flow to stick at high speeds".What does he mean by this?
ASIDE:Since I guess the representation of centre of pressure is pretty similar to curl,could someone please tell me why mathematicians use the gradient to represent curl?

As a engineer,I'm more used to seeing exercises where curl is calculated using the position vector 'dr' and then taking the line integrals.How can I prove that the gradient x field=line integral stuff ???
Thanks.

Last edited: Jul 23, 2012
2. Jul 23, 2012

### Simon Bridge

Center of pressure is like a center of mass. In aircraft it is kinda where the wing's lift appears to be acting.
http://www.grc.nasa.gov/WWW/k-12/airplane/cp.html

The description in the documentary sounds like garbled rubbish to me. Clearly the air-brake changes the pressure distribution dramatically giving you a lot of drag which could be described as making the air stick ...

AFAIK. mathematicians represent curl as, well, curl. You mean $\text{curl}(\vec{V}) = \vec{\nabla} \times \vec{V}$? This is the differential form of the integral equations you are used to - they are easier to use in general. Multiply it out and see what happens.

Gradient is like this: $\text{grad}V=\nabla V$ and the other one is the divergence: $\text{div}(\vec{V}) = \vec{nabla}\cdot\vec{V}$

Last edited: Jul 23, 2012