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# Mechanics help watch

1. I need help in resolving Horizontally and taking moments about A.
Ill take a pic of the question and what I have done so far which is not much..
http://mathsathawthorn.pbworks.com/f...cimen+2005.pdf
Q4 , i have started resolving horizontally have got N=something but what is the something and is it cos or sin alpha?
2. (Original post by English-help)
I need help in resolving Horizontally and taking moments about A.
Ill take a pic of the question and what I have done so far which is not much..
http://mathsathawthorn.pbworks.com/f...cimen+2005.pdf
Q4 , i have started resolving horizontally have got N=something but what is the something and is it cos or sin alpha?
Are you sure it involves taking moments about A? Nothing says the ladder is attached at that point.

First work out the angles the ladder makes with the floor and wall.

Once those angles are known, the rest should come fairly easily. You just need to find the horizontal and vertical components of the weight of the ladder which acts on the wall and floor.

Hint - Note also that the tension of the rope only needs to act in a horizontal direction.
3. (Original post by Pessimisterious)
Are you sure it involves taking moments about A? Nothing says the ladder is attached at that point.

First work out the angles the ladder makes with the floor and wall.

Once those angles are known, the rest should come fairly easily. You just need to find the horizontal and vertical components of the weight of the ladder which acts on the wall and floor.

Hint - Note also that the tension of the rope only needs to act in a horizontal direction.
I find mechanics very hard and struggle with it but my teacher told me we could do it the moments way by Resolving horizontally , then taking moments , then do moments of A to work out the horizontal component which I have named A, could you show me what way you would start it please?
4. (Original post by English-help)
I find mechanics very hard and struggle with it but my teacher told me we could do it the moments way by Resolving horizontally , then taking moments , then do moments of A to work out the horizontal component which I have named A, could you show me what way you would start it please?
Ah right ok, I understand what your teacher means.

If something is in equilibrium, it means it's not moving and it's also not rotating.

If it's not rotating, then it means the sum of all the moments comes to zero.

Treat A as the pivot, then look at the two points that can cause a moment: point B and point C.

I would start by working out the moment caused by point B. Can you work that out? It should require two trigonometric calculations.

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