Air is flowing in a wind tunnel at 8°C and 86 kPa at a velocity of 235 m/s. The Mach number of the flow is
A)0.54
B)0.87
C)2.1
D)1.4
E)0.70

Question

Quizplus · Accepted Answer

Solved by EES Software. Solutions can be verified by copying-and-pasting the following lines on a blank EES screen. 
k=1.4
Cp=1.005 "kJ/kg.K"
R=0.287 "kJ/kg.K"
T1=8+273 "K"
P1=86 "kPa"
Vel1=235 "m/s"
VS1=SQRT(k*R*T1*1000)
Mach=Vel1/VS1
"Some Wrong Solutions with Common Mistakes:"
W1_Mach=Vel1/VS2; VS2=SQRT(k*R*(T1-273)*1000) "Using C for temperature"
W2_Mach=VS1/Vel1 "Using Mach number relation backwards"
W3_Mach=Vel1/VS3; VS3=k*R*T1 "Using wrong relation"

Air Is Flowing in a Wind Tunnel at 8°C and 86