# Calculate the ratio of drag force on a jet flying at 1200km/h at an altitude of 15km to the drag force on a prop driven transport flying at half that speed and altitude. The density of air is 0.38 kg/m^3 at 15 km and 0.67 kg/m^3 at 7.5 km?

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Assume that the airplanes have the same effective cross-sectional area and drag

coefficient C.

Assume that the airplanes have the same effective cross-sectional area and drag

coefficient C.

##### 1 Answer

Jun 3, 2018

We know that drag force

#D=1/2CrhoAv^2#

where#C# is drag coefficient,#rho# is density of fluid in which object moves

Ratio of drag forces

#R=(1/2Cxx0.38A(1200)^2)/(1/2Cxx0.67A(600)^2)#

#=>R=(0.38(1200)^2)/(0.67(600)^2)#

#=>R=2.3# , rounded to one decimal place.