What is the drag force on a missile at low altitude?

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Homework Help Overview

The discussion revolves around calculating the drag force on a missile, specifically one with a diameter of 48 cm, traveling at a speed of 270 m/s at low altitude, with given air density and drag coefficient.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the formula for drag force and question the application of the diameter in the calculation. There are inquiries about how to correctly calculate the cross-sectional area of the missile, with suggestions to consider its cylindrical shape.

Discussion Status

The discussion is ongoing, with participants clarifying the interpretation of the problem and addressing the correct use of the diameter in calculations. Guidance has been offered regarding the assumption of the missile's shape.

Contextual Notes

There is a focus on understanding the distinction between diameter and cross-sectional area, and the implications of these terms in the context of the problem. Participants are navigating the assumptions necessary for the calculations.

djester555
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Homework Statement


Missile Calculate the drag force on a missile 48 cm in diameter cruising with a speed of 270 m/s at low altitude, where the density of air is 1.2 kg/m3. Assume C = 0.75.



Homework Equations



Fd = -1/2p(v^2)CA

The Attempt at a Solution



-1/2(1.2)(270^2)(0.75(0.48) = -15746.4 what am i doing wrong?
 
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0.48 is the diameter, not the cross-sectional area of the missile.
 
how do i calculate cross-sectional area?
 
djester555 said:
how do i calculate cross-sectional area?
Err...
Well, the usage of the term 'diameter' and general impression of the appearance of the missile should clearly hint towards approximating it as a cylinder / having a round cross-section at least.
 
The question mentions diameter, so you're supposed to assume the missile is a cylinder.
 

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