2. A mass-spring system oscillates with a frequency of 20 Hz. What is the period?

Current supplied to consumers from generating plants like coal power plant, nuclear power plant, geothermal and others are in form of alternating current instead of direct current because it can be transported easily in a long distance. also, the alternating current has a wide range of frequency and the amount or energy can be increased or decreased.

Jenny and fred both play a long note on their trombones. a stationary observer hears the sound increasing and decreasing repeatedly in loudness. which of these must be true? the sound waves from the two trombones have slightly different frequencies.the sound waves from the two trombones have the same frequency.the sound waves from the two trombones have slightly different amplitudes.the sound waves from the two trombones have the same wavelength.the sound waves from the two trombones have slightly different velocities.  lolthe answer is          the sound waves from the two trombones have slightly different frequencies.

Ithink it would be a concave lens.