The compass in a light aircraft shows that it is flying due north. The air speed indicator gives a reading of 150km/h. If there is a 50km/h wind blowing from west to east, what is the ground speed of the aircraft?

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- Jul 18th 2006, 12:49 PM #1

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- Jul 18th 2006, 02:40 PM #2Originally Posted by
**bobby77**

use pythagorean theorum...

$\displaystyle c=\sqrt{150^2+50^2}$

$\displaystyle c=\sqrt{22500+2500}$

$\displaystyle c=\sqrt{25000}$

$\displaystyle c=50\sqrt{10}\approx158.114$

- Jul 18th 2006, 07:57 PM #3

- Jul 18th 2006, 08:01 PM #4

- Jul 18th 2006, 08:17 PM #5Originally Posted by
**Quick**

Draw a horizontal line and a line perpendicular to it(it will be obviously vertical).Label horizontal as x , vertical as y. Then z will be upwards out of the plane of the paper.

In the question

velocity of plane (without air)=0i+150j+0k

velocity of air=50i+0j+0k

resultant velocity=50i+150j+0k

(Actually there is a method which could tell you that the cordinate system used by you is acc. to international convention or not(based on cross product of vectors))