# Help with a level forces question

I would like some help for with question 10, iii, b (attached below)
i dont understand how they have got the answer (on the ms)
(edited 2 months ago)
Original post by firestudent
I would like some help for with question 10, iii, b (attached below)
i dont understand how they have got the answer (on the ms)

Original post by firestudent
I would like some help for with question 10, iii, b (attached below)
i dont understand how they have got the answer (on the ms)

They have found the resolved horizontal and vertical components of the two remaining forces (taking rightwards and downwards as the positive directions), then found the inverse tangent of (vertical component) / (horizontal component).
(edited 2 months ago)
Original post by old_engineer
They have found the resolved horizontal and vertical components of the two remaining forces (taking rightwards and downwards as the positive directions), then found the inverse tangent of (vertical component) / (horizontal component).

how does this give the angle below the horizontal?
Original post by firestudent
how does this give the angle below the horizontal?

If you draw a sketch of the horizontal and vertical components it should become clear. The resultant force acts along the diagonal of the usual parallelogram of forces (in this case a rectangle of forces).
Does this diagram help?

Spoiler

the only horizontal force is from 3sin(theta) and the only vertical forces are 3cos(theta) and P, so the horizontal resultant force (x) and vertical resultant force (y) is.... and so the alpha is...

edit: sorry @old_engineer I didnt mean to spoil your hint 😥
(edited 2 months ago)
Original post by old_engineer
If you draw a sketch of the horizontal and vertical components it should become clear. The resultant force acts along the diagonal of the usual parallelogram of forces (in this case a rectangle of forces).

thank you, i've understood now
Original post by mosaurlodon
Does this diagram help?

Spoiler

the only horizontal force is from 3sin(theta) and the only vertical forces are 3cos(theta) and P, so the horizontal resultant force (x) and vertical resultant force (y) is.... and so the alpha is...
edit: sorry @old_engineer I didnt mean to spoil your hint 😥

thanks, out of interest how would the sin rule work to get this answer, as shown in the extreme left hand column?