# CURRENT AFFAIRS

## 2018

 Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Supersonic travel is a rate of travel of an object that exceeds the speed of sound. What is speed of sound in dry air at 20 degree Celsius?
 A 343 m/s B 343 Km/s C 331.2 m/s D 331.2 Km/s
Explanation:

Detailed explanation-1: -Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately 343.2 m/s (1,126 ft/s; 768 mph; 667.1 kn; 1,236 km/h).

Detailed explanation-2: -The speed of sound is about 768 miles per hour (1,236 kilometers per hour) at sea level. These speeds are referred to by Mach numbers. The Mach number is the ratio of the speed of the aircraft to the speed of sound. Flight that is faster than Mach 1 is supersonic.

Detailed explanation-3: -When the speed of any object exceeds the speed of sound in air (330 m s-1) it is said to be travelling at supersonic speed.

Detailed explanation-4: -supersonic flight, passage through the air at speed greater than the local velocity of sound. The speed of sound (Mach 1) varies with atmospheric pressure and temperature: in air at a temperature of 15 °C (59 °F) and sea-level pressure, sound travels at about 1,225 km (760 miles) per hour.

Detailed explanation-5: -As an aircraft flies at supersonic speeds it is continually generating shock waves, dropping sonic boom along its flight path, similar to someone dropping objects from a moving vehicle. From the perspective of the aircraft, the boom appears to be swept backwards as it travels away from the aircraft.

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