At 01:58 pm 06/05/2006 -0600, you wrote: >Grimer wrote. >> >> You seem very fond of calculating things, Fred. How about >> working out the relation between size and power output? >> >Actually at the optimum 0.2 Torr pressure for the Radiometer >the kinetic theory equation for the number of atoms-molecules >striking a unit surface area per second is: > >0.25 * (N/V) * v *Area > >At 760 torr 300 K, N/V = 2.69E25 atoms-molecules per cubic meter >1/2 mv^2 = kT, for Argon-40 v = [4.14E-21/(0.5*40*1.66E-27)]^1/2 = >353 meters/sec. >At 0.2 torr N/V = 7.07E21 atoms-molecules per cubic meter. > >So, 0.25 * 7.07E21 * 353 = 6.24E23 molecules/meter^2 per sec. > >Recoil mv = 2 * 6.24E23 * 40 * 1.66E-27 * 353 = 0.083 newtons/meter^2 force > >Not much torque there,if I didn't goof, Frank. > >Fred
I fear you might have Fred since I believe that the mechanism of operation of the radiometer is a bit different from the one you seem to be assuming. Something to do with the edges of the vanes and molecules percolating and them IIRC. Frank
