Challenging M1 Question - Vectors with Moments

[vanibharutham]

Hey guys,

Here is an M1 question involving both moments and vectors taken from a Solomon Paper..

I can't see an easy way of solving this question, but i had to use some C4 and some vector calculus... if you guys see an easy way please tell me

4. The force F₁ = (5i + 2j) N acts at the point A on a lamina where the position vector of A,
relative to a fixed origin O, is (3i – 2j) m.
(a) Calculate the magnitude and the sense of the moment of the force about O. (4 marks)

Another force F₂ = (pi + qj), acts at the point B with position vector (–i + 4j) m so that the
resultant moment of the two forces, F₁ and F₂, about O is zero.
Given also that the moment of F2 about A is 34 Nm in a clockwise sense,

(b) find the values of p and q. (6 marks)

[astarmathsandphysics]

Where is this question? can you post a link to the paper

[halosh92]

could u atleast post the final answers so that we could cross check?
thx

[vanibharutham]

http://www.freeexampapers.com/FreeExamPapers.com_.php?__lo=QSBMZXZlbC9NYXRocy9FZGV4Y2VsL00xL1NvbG9tb24vU29sb21vbiBDLnBkZg== Here is the link for the paper


and the answers are

a) 16 Nm anticlockwise
b) p = 3 and q = 4

i used the cross product method...