G Force

[kermit911]

I have a Hovercraft and it spins a fan at 6500 rpm or 108.3 revolutions per second. There are 6 fan blades, the length of one fan blade is 16 inches. The total length from the tip of one fan blade to the tip of the other fan blade is 40 inches. How many G forces are these fan blades generating?

[Space]

fans don't generate "G forces",
they generate pressure and/or airflow.

What you can do is search for a fan of similar size and speed on a manufacturer's website ( example: papst )
There you may find the specifications, such as: the maximum pressure the fan can generate, and the maximum airflow it can generage.

now are we talking about the fan that is below the hovercraft, or a propulsion fan ?

[kermit911]

Talking about the fan that Propels the craft. I thought since the fan is spinning don't the tips of the blade affected by g-forces?

[mibn2cweus]

The g-force at a radius of 20 inches for a constant 6500rpm would be about 24000 times the force of gravity at the surface of the Earth.

[Gnu]

The acceleration at the tip of the blade is rw^2. The radius is 20 inches, or 50cm = 0.5m. w is the angular velocity, which is 108*2*pi radians per second, or 678 radians per second. Therefore the acceleration is 0.5 metres x 678^2, or about 230 000 metres per second squared.
This gives mibn2cweus's result.

[Peter Pedant]

Yeah I think they just want you to use
F = mrw2

and then to say that g is 9.81 so divide everything by that

must be an engineering question, all the physicists would go crazy to see Newton being slapped around like this

[mibn2cweus]

He (Sir Isaac) started it!