Hi, I am having troubles with a question concerning relative motion. The problem goes:(adsbygoogle = window.adsbygoogle || []).push({});

A plane is travelling at an air speed of 285 km/h [E45ºS]. A wind is blowing to the northeast at 75 km/h [N22ºE] relative to the ground. Determine the velocity relative to the ground.

My teach prefers that we do not use the cosine law to determine the unknown vector, and instead requests that when we draw our diagram, we do something called the resolution of vectors. Which is separating the two vectors into x and y components, add the x's and y's together and use Pythagorean theorum to solve.

The cosine law provided me with the correct answer for this question, which was 265 km/h.

However, in using his method, my diagram (which was correct, and I have attached, to anyone who is confused), resembled a rectangle, and I came up with these calculations:

285/sin90 = x1/sin45

x1 = 202 km/h

x2/sin22 = 75/sin90

x2 = 28 km/h

Therefore, shouldn't x1 + x2 = 265 km/h ?

Please help me!

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Vectors and Relative Motion

**Physics Forums | Science Articles, Homework Help, Discussion**