Assertion (A): A jet aircraft moving at Mach Number equal to 1 travels faster at an altitude of 15 km than while moving at Mach Number equal to 1 near the sea level. Reason (R): The velocity of sound depends on the temperature of the surrounding medium.
✓ Correct answer: d) A is false but R is true
ExplanationMach Number is the ratio of an object’s speed to the speed of sound in the surrounding medium: Mach Number = Object’s Speed / Speed of Sound The speed of sound in air is primarily influenced by temperature and to a lesser extent by atmospheric composition.Assertion (A) is false: The speed of sound depends on the temperature of the medium.At higher altitudes (e.g., 15 km) the temperature is much lower than at sea level.The speed of sound decreases with decreasing temperature.Therefore, at 15 km altitude, the speed of sound is lower than at sea level.If the aircraft is moving at Mach 1 at both altitudes, its actual speed will be lower at 15 km because the speed of sound is lower there.Reason (R) is true: The velocity of sound depends on the temperature of the surrounding medium.This is also true because the speed of sound is given by v=√γRTM, where γ is the specific heat ratio, R is the gas constant, T is the absolute temperature and M is the molecular mass of the gas.A decrease in temperature reduces the speed of sound.Directions: The following two items consist of two state
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