Question

What is the airspeed relative to the ground of an airplane with an airspeed of 120km/h when it is in a 90-km/h crosswind?

Answer 1

You should draw a vector diagram for this. Using a scale of say 1cm=10km/hr.

Draw a straight line up the page 12cm to represent northwards at 120km/hr.

Where this line finishes, draw a line from left to right 9cm long to represent a crosswind of 90km/hr.

Once you've done that, draw a line from the very start point to the end point, giving you a triangle.

Measure it's length, it will be 15 cm long, meaning that the airplane is actually flying in a north-easterly direction at 150km/hr. the line you've drawn actually shows you the path the aircraft would fly in those conditions.


You could also use math to work out the speed (remember you've just drawn a right angled triangle)

The hypotenuse will be the speed of the aircraft.

x^2 = 120^2+90^2
x^2 = 22500
x = 150