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1. OK here is a question I'm very much stuck on from the Jan '06 paper:

4) Two forces P and Q act on a particle. The force P has a magnitude 7N and acts due North. The resultant of P and Q is a force of magnitude 10N acting in a direction with bearing 120 degrees. Find:
(i): The magnitude of Q
2. (Original post by Ultimate1)
OK here is a question I'm very much stuck on from the Jan '06 paper:

4) Two forces P and Q act on a particle. The force P has a magnitude 7N and acts due North. The resultant of P and Q is a force of magnitude 10N acting in a direction with bearing 120 degrees. Find:
(i): The magnitude of Q
Meh, I wouldn't say this was that 'easy' (relative to other M1 questions).

Nevertheless, First draw what's happening (the way you draw it might depend on which method you intend to use).

I would do it by resolving the forces horizontally and vertically. The difference between P and R is Q (for example, all of R's horizontal component is from Q, and P is acting north).

Once you know the component of Q, it's just pythagoras for it's magnitude and some trig for the angle.

Note you can do it with cosine rule - just as effective, but it's not my preferred method.

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