Re: Physics/Math
posted by COFFEE .
Calculate the ratio of the drag force on a passenger jet flying with a speed of 750 km/h at an altitude of 10 km to the drag force on a propdriven transport flying at onefifth the speed and half the altitude of the jet. At 10 km the density of air is 0.38 kg/m3 and at 5.0 km it is 0.67 kg/m3. Assume that the airplanes have the same effective crosssectional area and the same drag coefficient C.
(drag on jet / drag on transport.
Please help :)
* Physics/Math  bobpursley, Saturday, February 10, 2007 at 7:13pm
You must have been given some equations for drag force, these equations vary, but typically they depend on Area, a coefficeint, and velocity^2.
Post your equations and work, and I will critique.
* Physics/Math  COFFEE, Saturday, February 10, 2007 at 9:54pm
Sorry, the equation given is:
D=1/2(Dp)(Area)(Velocity^2)
I do not understand what area I am trying to calculate and what the constant equals. How do I find Dp and Area???
You don't need area. Dp is density.
You are calcualting the ratio of drag for th jet as compared to the prop plane.
Forcejet/forceprop=densityjetair*vj^2 /densityprop*vp^2
Notice all the units divide out. The donstant is notshowing, but it divides out anyway.
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