# feb29 - MIT OpenCourseWare http/ocw.mit.edu 6.055J 2.038J...

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Unformatted text preview: MIT OpenCourseWare http://ocw.mit.edu 6.055J / 2.038J The Art of Approximation in Science and Engineering Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms . 32 6.055 / Art of approximation 5.4 Drag This section section contains a proportional-reasoning analysis of drag – using a home ex- periment – and then applies the results to jumping ﬂeas. 5.4.1 Home experiment using falling cones Here is a home experiment for understanding drag. Photocopy this page and cut out these templates, then tape the edges together to make a cone: r = 1in cutout=90 ◦ r = 2in cutout=90 ◦ If you drop the small cone and the big cone, which falls faster? In particular, what is the ratio of their fall times t big / t small ? The large cone, having a large area, feels more drag than the small cone does. On the other hand, the large cone has a higher driving force (its weight) than the small cone has. To decide whether the extra weight or the extra drag wins requires finding how drag depends on the parameters of the situation. However, finding the drag force is a very complicated calculation. The full calculation requires solving the Navier–Stokes equations: ( v · r ) v + ∂ ∂ v t = − ρ 1 r p + ν r 2 v ....
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feb29 - MIT OpenCourseWare http/ocw.mit.edu 6.055J 2.038J...

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