Final answer:
To calculate the drag force on a cylinder with air blowing at it, one must use the drag force equation incorporating the drag coefficient, air density, frontal area, and velocity. However, the needed values for air density and drag coefficient at 820°C are not provided, so a precise numerical answer cannot be given.
Step-by-step explanation:
The student's question involves calculating the drag force on a cylinder in a fluid flow scenario. To calculate the drag force on a 60-cm-diameter, 6-m-long cylinder with 820°C-air blowing normal to its axis at 40 km/h, one would need to use the drag force equation Fdrag = ½CDρAv², where CD is the drag coefficient, ρ is the density of the air, A is the frontal area of the cylinder, and v is the velocity of air. However, additional information such as the drag coefficient and air density at 820°C is required to perform an accurate calculation.
In this case, due to the temperature of the air, the standard air density would not apply, and the drag coefficient might also be different due to changes in the air properties at high temperatures. Both the drag coefficient and density might need to be obtained from empirical data or calculated based on the air properties at the given temperature.
Without the specific values for the drag coefficient and air density at 820°C, an exact numerical answer is not possible. However, the physics concept applied and the process remain consistent: calculating drag force requires an understanding of physical properties and fluid dynamics principles.