Question1
Submarine (when at rest underwater) uses a sonar device that sends 20 kHz sound pulses downward from bottom of it. It detects two echoes; one coming from another submarine that is directly underneath and moving in the upward direction at a speed vs and other coming from ocean ground. If the detected beat frequency is 400 Hz, find the speed of the approaching submarine in km/h. Take the speed of radar waves in sea water as 980 m/s.
Question2
If the inner and outer radii of groove on an LP are 10 cm and 5 cm, what is the linear speed of the phonograph needle at the beginning and at end of play, respectively? (A standard LP rotates at the speed of 33.3333 rev/min.)