A sound note of frequency 250 Hz and wavelength 1.3m is produced at a point near a hill. If the echo of the sound is received 1 second later at the point, how far away is the hill from the point?
What is the escape velocity of a body on the surface of the earth of radius R if the gravitational constant is G and the mass of the earth is M? (Neglect energy losses to the surroundings)
