Thread: vector resultant

find the magnitude and direction of the resultant of two vectors u and v with magnitudes of 6 and 2 and an angle of 140 between them.

i got |u+v|=7.64 units and the direction to be 9.69 deg, is it right?

You can make a sketch, and complete the parallelogram of forces.

From this, the magnitude of the resultant forces is given by the cosine rule, taking the sides 6 and 2 and the angle (180-140) = 40 degrees.



Can you try out again on the direction now?

i get 4.64 units and 16 deg

That's it!

Well done.

Here's a picture to see where the 40 degrees came from: