Question

Physics 12 Equilibrium question!

Answer 1

The initial instinct is to just add the two vectors together to get R. And here's why I think it's not going to work out:

Intuitively, adding V1 and V2 would obviously NOT give you the answer! If you add V1 and V2 together, the resultant you get from the addition would be a greater than the resultant you're supposed to get!

Answer 2

Instead, notice how it's a triangle. Given the values of each "leg" of the triangle, you can easily find the value of V1 and V2.

And now you might be asking: now what?

Recall your cosine rule. You can use it when you're given a triangle that doesn't contain special properties (e.g. triangles with 90-degree angles, isosceles triangles). All you need is the value of two sides and the angle in between! (See the attachment.)

You can then find the angle in between V1 and V2 by finding the angles like so:



And you know that a line is 180-degrees across!

I hope this helps.