Finding the direction and velocity of wind using vectors question

[shy9488]

Homework Statement

A person, traveling eastward at a rate of 4.0 km/hr, observes that the wind seems to blow directly from the north; on doubling his speed the wind appears to come from the northeast; determine the direction of the wind and its velocity.

Homework Equations

The Attempt at a Solution

My teacher has actually given us the answers on this question. However, I am stuck at the point where she says the
Velocity of wind relative to person = Velocity of wind relative to the ground - velocity of person relative to the ground.

I just can't understand this at all! Please help!
Thank you in advance!

 

[tiny-tim]

welcome to pf!

hi shy9488! welcome to pf!

… I am stuck at the point where she says the
Velocity of wind relative to person = Velocity of wind relative to the ground - velocity of person relative to the ground.

I just can't understand this at all! Please help!

it means that if you draw the three vectors (with arrows), then they join up to form a vector triangle

(and when the question says "observes that the wind seems to blow directly from the north", it means that the velocity of the wind relative to the person is north)

see the pf library, or wikipedia, for details ​