The speed of sound in air depends on temperature according to the approximate expression
Where Tc is the celsius temperature. In dry air, the temperature decreases about 1-degree Celsius for every 150-m rise in altitude. Assume this change is constant up to an altitude of 9000m. What interval is required for the sound from an aeroplane flying at 9000 m to reach the ground on a day when the ground temperature is 30 degrees celsius.
