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## Mach Number Activity

Open the slide called Mach Number and read the definition of Mach number.

Various military aircraft have Mach numbers from 1.6 to over 3. Do you know what that means?

The unitless Mach number was named after the Austrian physicist Ernst Mach. The Mach number is ratio of the speed of the aircraft to the speed of sound . An airplane flying at less than Mach 1 is traveling at subsonic speeds; at about Mach 1, or transonic , it is at the speed of sound, and greater than Mach 1 is supersonic . An aircraft traveling at Mach 2 is traveling at twice the speed of sound.

The speed of sound on an average day at sea level is 761 mph. The speed of sound depends on the composition and temperature of the air and it decreases with altitude. For the following problems, assume that the speed of sound is constant and equal to 740 mph.

1. Use the definition of Mach number obtained from the Mach Number slide and the information above to determine the speed of a jet at Mach 3.

2. Convert the speed of sound units of mph to km/hr.

3. Let's find the top speed of some interesting jets. The maximum Mach number of the jets listed can be found on the World Wide Web. Simply go to the link provided, B-747, F-18, and SR-71A. Use the data to fill in the Mach number, then compute and fill in the speeds in the table below.

Jet
Max Mach Number
Max Speed, km/hr
B-747

F-18

SR-71A

4. The X-15 was a research aircraft designed and built for NASA. Using its maximum Mach number, compute its maximum speed.

Max Mach Number, = __________________

Max Speed , km/hr = ______________________

Related Pages:
Standards
Worksheet
Lesson Index
Aerodynamics Index

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