Q. At a factory, a noon whistle is sounding with a frequency of 490 Hz. As a car traveling at 77 km/h approaches the factory, the driver hears the whistle at frequency fi. After driving past the factory, the driver hears frequency ff. What is the change in frequency ff - fi heard by the driver? (Assume a temperature of 20° C.)
Q. Suppose that in a particular vacuum tube the potential of the anode is 340 V higher than that of the cathode. If an electron leaves the surface of the cathode with zero initial speed, what is its speed when it strikes the anode? (m/s)