M1 question pleeeeease help

For ii) try resolving horizontally to the right F=ma but since it's in eqm, it will be F=0 (all forces add up to 0)
Tension goes away from the box

Resolve the forces horizontally and vertically. that might help.

Hi thanks!! So I resolved the forces -could you please kindly let me know the next step? Many thanks

this what I got, not sure if it's right
(excuse the bad handwriting 😩)

this what I got, not sure if it's right
(excuse the bad handwriting 😩)

well the body is in equilibrium so horizontally BA = BC so you can use simultaneous equations to solve the tensions.

You could also solve vertically, either way should work

The alternative is to use the triangle of forces. It is isosceles, so that givesTBC = 400 straight off. Then use sine or cosine rule to find the other tension.

this what I got, not sure if it's right
(excuse the bad handwriting 😩)

Please DO NOT post full solutions - it's against forum rules

I might sound dumb but I don't get how to use triangle of forces with this lol

ah I didn't know that, so sorry
where can I read all the rules ?

well the body is in equilibrium so horizontally BA = BC so you can use simultaneous equations to solve the tensions.

You could also solve vertically, either way should work

Could you please kindly let me know how to do it the triangle of forces way?
I have drawn the triangle which took some time (as in getting the angles in the right places) and then the ms just confused me

I've never actually used a triangle of forces but it looks like you could use the cosine or sine rule to solve each side because you have 3 angles and 1 side so yeah, try the sine rule first.

Thanks!
And for part iii) I can't figure what the ms is trying to say (it's a statement question) could you please kindly help with this too thank you so much

I think it's saying that the vertical forces are now unbalanced when alpha is 60. so the weight component which acts downwards is greater than the tension component which acts upwards against the weight, hence there is a resultant force downards hence the body is not in equilibrium.

as angle BC to the vertical is constant, it must be the vertical component of AB which is affected by the change in angle so prove that the vertical component of AB is less than the weight