When discussing the speed of a body in relation to the speed of sound, we are referring to the Mach number. The Mach number is a dimensionless quantity that represents the speed of an object moving through a medium, typically air, compared to the speed of sound in that medium.

For example, if an object is traveling at the speed of sound, its Mach number would be 1. Anything traveling faster than the speed of sound would have a Mach number greater than 1, while anything traveling slower would have a Mach number less than 1.

The speed of sound varies depending on the medium through which it is traveling, with the speed of sound in air at sea level being approximately 343 meters per second. Therefore, if an object is traveling at 686 meters per second, it would have a Mach number of 2, indicating that it is moving twice as fast as the speed of sound in air.

Understanding the Mach number is crucial in fields such as aviation, where aircraft speeds are often expressed in terms of Mach numbers. For example, an aircraft traveling at Mach 2 would be moving twice as fast as the speed of sound in the surrounding air.

It is important to note that exceeding the speed of sound can lead to the formation of shock waves, resulting in a sonic boom. This phenomenon occurs when an object travels faster than the speed of sound, causing the sound waves it generates to overlap and create a sudden, sharp noise.

Overall, the Mach number provides a convenient way to compare the speed of an object to the speed of sound in a given medium. By expressing speed in terms of Mach numbers, we can easily understand how fast an object is moving relative to the speed of sound.

For more information on the Mach number and its significance, visit NASA's website or Britannica.

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