An aeroplane can fly at a velocity X when moving through still air. When flying in wind the aeroplane’s velocity relative to the ground is Y.

Question 9

An aeroplane can fly at a velocity X when moving through still air. When flying in wind the aeroplane’s velocity relative to the ground is Y.

Which vector diagram shows the magnitude and direction of the wind velocity W ?

Reference: Past Exam Paper – November 2016 Paper 11 & 13 Q3

Solution:

Answer: A.

This question is on finding the resultant vector graphically. This can be done by either the parallelogram method or the triangle method.

The method described below is the triangle method.

Velocity in still air = X

But in the presence of wind, the aeroplane’s velocity = Y

This is the resultant velocity vector.

So, when considering the velocity of the aeroplane in still air, X, and the effect of the wind velocity W, the resultant velocity vector is Y.

Y = X + W

Y is the resultant velocity vector of the aeroplane and the wind speed.

So, lay out the vector X.

The wind velocity vector W is added to X. This is done by placing the tail of W at the head of the X vector.

 
The resultant vector Y starts from the tail of X to the head of W.