Bernoulli demonstrations with Julius Sumner Miller....

[Jase T]

I have to say i love physics.

 

Watch and enjoy

 

 

 

 

[old man emu]

The good Professor says he is demonstrating of Bernoulli's principle, but this is incorrect. At 9:27 in the video he is demonstrating the Magnus Effect. It is not the velocity of the air, bit its viscosity - assumed to be negligible in Bernoulli's principle - that is central to understanding the magnitude of the force.

 

When a body (such as a sphere or circular cylinder) is spinning in a viscous fluid, it creates a boundary layer around itself, and the boundary layer induces a more widespread circular motion of the fluid. If the body is moving through the fluid with a velocity V, the velocity of the thin layer of fluid close to the body is a little less than V on the forward-moving side and a little greater than V on the backward-moving side. This is because the induced velocity due to the boundary layer surrounding the spinning body is subtracted from V on the forward-moving side, and added to V on the backward-moving side. If the spinning body is regarded as an inefficient air pump, air will build up on the forward-moving side causing higher pressure there than on the opposite side.

 

This video explains it well.

 

 

 

 

By the way, the Good Professor ignited my love of Science. I remember watching his "Why is it so" program on the ABC.

 

https://www.abc.net.au/science/features/whyisitso/about.htm#about