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Ch 03: Motion in Two or Three Dimensions
Chapter 3, Problem 3

An airplane pilot wishes to fly due west. A wind of 80.0 km/h (about 50 mi/h) is blowing toward the south. (a) If the airspeed of the plane (its speed in still air) is 320.0 km/h (about 200 mi/h), in which direction should the pilot head?

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Identify the given values: wind speed is 80.0 km/h south, and the plane's airspeed is 320.0 km/h.
Set up a vector diagram: Represent the wind velocity vector pointing south and the plane's airspeed vector pointing in the unknown direction that the pilot should head.
Use vector addition to find the resultant vector, which should point due west. The resultant vector is the vector sum of the plane's airspeed vector and the wind velocity vector.
Apply the sine and cosine rules to solve for the angle at which the pilot should head. This involves calculating the angle between the resultant vector (due west) and the airspeed vector of the plane.
Adjust the plane's heading to compensate for the wind. The angle calculated will tell the pilot the direction to head relative to north (or south) to ensure the actual flight path is due west.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Vector Addition

Vector addition is the process of combining two or more vectors to determine a resultant vector. In this scenario, the airplane's velocity and the wind's velocity are both vectors, with specific magnitudes and directions. The pilot must calculate the resultant vector to ensure the airplane travels due west, taking into account the southward wind.
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Relative Velocity

Relative velocity refers to the velocity of an object as observed from a particular reference frame. In this case, the pilot's airspeed is relative to the air, while the wind's speed is relative to the ground. Understanding relative velocity is crucial for determining the correct heading to counteract the wind's effect and maintain the desired course.
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Trigonometry in Navigation

Trigonometry is essential in navigation for resolving vectors into components. The pilot can use trigonometric functions to find the angle at which to head the airplane to counteract the wind. By applying sine and cosine functions, the pilot can determine the necessary heading to achieve a westward trajectory despite the southward wind.
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