Question

Race cars at the Indianapolis Speedway average speeds of 185 mi/h. After determining the altitude of Indianapolis, find the Mach number of these cars and estimate whether compressibility might affect their aerodynamics.

Answer 1

Answer:

- the Mach number is 0.24.

- Compressibility becomes effective when Mach number is greater than 0.3, the Mach number of the race cars is less than 0.3, hence, compressibility will not affect their aerodynamics.

Explanation:

Given the data in the question;

Average speed V = 185 miles per hour = ( 185 /2.237 ) m/s = 82.7 m/s

From Almanac, we can find that Indianapolis is at 220 m altitude.

So from table, at that altitude, the standard speed of sound will be 339.4 m/s .

Mach number of the race car will be;

Mach Number = Velocity / sound speed

we substitute

Mach Number = ( 82.7 m/s ) / ( 339.4 m/s )

Mach Number = 0.24

Therefore the Mach number is 0.24.

We know that, compressibility becomes effective when the Mach number is greater than 0.3.

Since the Mach number of the race cars is less than 0.3, compressibility will not affect their aerodynamics.