# Forces, 90% Trig

• Feb 4th 2010, 10:40 AM
alibond07
Forces, 90% Trig
Forces P, Q and R act on a particle at O in the plane of the coordinate axes 0x, 0y. Force P acts along 0x, Q acts along 0y, and R acts at an angle $theta$ with 0x, in the first quadrant. Calculate the magnitude of the resultant force and the angle it makes with 0x when:

P=3N
Q=4N
R=5N
$theta$= 60 degrees

I worked out the resultant force by resolving 'R' into horizontal and vertical forces, but you cant work out the angle it makes with 0x by doing this. I was hoping someone with more trig knowledge could help out.
• Feb 4th 2010, 11:34 AM
Henryt999
Just curious
Or the angle was $60^0$?
My mistake sorry, why cant you work out the angle?
I never seen notations like 0x 0y? does that mean..0x = along the x-axis?

If you worked out the resulting force just draw a picture.
Use the tip to tail method with the vector and you should be able to calculate the angle. You will have to sides and a right angle triangel.
Assuming you have a vector along the x-axis and one along the y-axis + your vector R (split inte $x;y$ its components).
I got a bit confused by the notations you are using 0x;0y sorry if I missread the question..?Did I?
Hope it helped otherwise(Rock)