Calculate the ratio of the drag force on a passenger jet flying at an altitude of 10 km to the drag force on a prop-driven plane flying at two-fifths the speed and half the altitude of the jet. At 10 km the density of air is 0.380 kg/m3 and at 5.0 km it is 0.670 kg/m3. The prop-driven plane has one-third the cross-sectional area of the passenger jet. The passenger jet has two-fifths the drag coefficient of the prop-driven plane.

Respuesta :

Answer:

2.268

Explanation:

The concepts that we need to use here for give a solution are Drag coefficient and drag force.

Drag force is given by,

[tex]F_D = \frac{1}{2} c \rho A V^2[/tex]

Where,

c is the drag coefficient

[tex]\rho[/tex] is the density

A cross sectional area

V the velocity.

Our values for this problem are divided for Passenger and Driver.

For Jet are:

[tex]V_1 = 1000km/h \\h_1 = 10*10^3m\\\rho_1 =0.38kg/m^3[/tex]

For prop-driven are:

[tex]V_2 = 500km/h\\h_2 = 5km\\\rho_2 = 0.67kg/m^3[/tex]

From the problem we need to assume that [tex]A_1 = A_2[/tex] and [tex]c_1 = c_2[/tex], THEN

Applying to each case the Drag force equation we have,

[tex]F_{D1} = \frac{1}{2} \rho_1 V^2_1\\F_{D2} = \frac{1}{2} \rho_2 V^2_2[/tex]

The ratio between the two force is,

[tex]\frac{F_{D1}}{F_{D2}}=\frac{\rho_1 V^2_1}{\rho_2 V^2_2}\\\frac{F_{D1}}{F_{D2}}=\frac{0.38*1000^2}{0.67*500^2}\\\frac{F_{D1}}{F_{D2}}= 2.268[/tex]

Therefore the force experienced by a Jet pilot under these conditions is 2,268 times greater than that of a prop-driven