Doppler Effect – Anyone done any measurements?

By Friday, February 18, 2011 , , , 0

Like most Physics teachers, I do several demos of the Doppler Effect in class but I never take any quantitative measurements.  The following YouTube clip of a fire engine has terrible video but the effect is very noticeable. Fire Engine - Doppler Effect I was wondering if anybody has ever loaded soundfiles into their computer and done the Fourier analysis to measure the frequencies observed during a Doppler Effect demo.  While Fourier analysis would give the best results (Audacity is free and ...

Reverse Friction?

By Tuesday, January 18, 2011 , , , , 0

I have always thought of friction as being a physics topic but it has been proposed by scientists in the University of California that a chemical force could be used to reduced friction. Chemical force? What do I mean by this? I am writing about intermolecular forces, the force that 'holds' atom or molecules together. As you know there are three intermolecular forces: Hydrogen bonds (the strongest). Permanent dipole - dipole interactions. Van der Waals / London dispersion forces (the weakest). It is the Van der Waals ...