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Physics Education

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1 Benenson, R. E. MOLECULAR VELOCITY DETERMINATION THROUGH GAS EFFUSION: INTERMEDIATE LABORATORY EXPERIMENT (In American Journal of Physics -- January 1969 -- Volume 37, Issue 1, Pp. 39)
New York American Institute of Physics. American Journal of Physics 1969 First Edition Thus Wrappers Very Good 
Thin 4to 11" - 13" tall; 7 pages; We are offering the entire issue which contains this article. An experiment is described to determine the average velocity of gas molecules in a container while effusion takes place through a small hole into vacuum. When the mean free path of the molecules becomes large compared to the hole diameter, the measurement of pressure as a function of time permits the average velocity to be extracted. The equipment and procedure are simple, and an agreement to within 10% of the kinetic theory of gas value has been obtained using an inexpensive McLeod gauge. The experiment has been performed using air, helium, and argon; measurements on air and helium were performed both at room and dry ice temperatures. A formula has been derived to take into account the effect of outgassing of the container walls at low pressures. Average velocities may be extracted either by a hand calculation between pairs of data points, or by using a short computer program for least-squares analysis. A derivation is given in an Appendix for the effect on the effusion of the hole being drilled in a wall of thickness small, but not negligible, compared to the hole diameter. During the initial pump-down period, while the container pressure is still comparable to atmospheric, the pressure-versus-time data can be analyzed in terms of hydrodynamic theory and used to deduce a virtual hole area for the streaming molecules. Measurements of pressure-increase with time in a sealed-off system gave poor agreement with the rate of outgassing needed to fit the effusion data." 
Price: 200.00 USD
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2 Timmermann, Hans SCHULPHYSIK ALS VOLKISCHES LEHRGUT (Völkisches Lehrgut. Schriftenreihe Zur Neugestaltung Des Volksschulunterrichts).
Leipzig Julius Klinkhardt 1934 Stiff Wrappers Very Good+ with no dust jacket 
8vo; 96p. pages; With small German high school library stamp and paper label at heel of spine. 
Price: 70.00 USD
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