Amplifiers Earthquake Of San Francisco For Sale I Have 3 More Questions That I Need Help On?

I have 3 more questions that I need help on? - amplifiers earthquake of san francisco for sale

A) If an earthquake occurs, produces two types of sound waves and through the country. The primary or P wave has a speed of 8.00 km / s, and the secondary or S wave has a speed of about 5.22 kilometers per second, a seismograph, located at a distance, the records of the arrival the P-wave, then, 82.5 s later, the record of the arrival of the S wave of adoption that the waves travel in straight lines, how far is the seismograph to the earthquake?

B) The volume control on a stereo amplifier is adjusted so that the noise level increases the intensity from 28.7 to 56.9 dB. What is the relationship between the intensity of the recent intensity of their origins?

C) aSource ripples produced on the surface of a lake. The waves have a wavelength of 12.0 m and travels outward at a speed of 6.67 m / s. You are in a boat with a speed of 4.09 m / s directly to the source of the wave. What is observed in the frequency of the waves?