a level physics question -a uniform ladder

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o_reo
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#1
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#1
A uniform ladder AB of m=20.0kg rests in equilibrium. A is in contact with a smooth vertical wall and B is in contact with a rough horizontal floor. The ladder lies in a vertical plane perpendicular to the wall and makes an acute angle α=25.0
to the horizontal. A horizontal force P=400N is applied to the ladder in a direction away from and perpendicular to the wall. This force acts at the point one quarter of the way up the ladder.

question
Find, in terms of P, m and alpha,α, the magnitude of the normal reaction force at A, N subscrpit A

and calculate its value.

What I have done:
I have drawn the diagram but don't know how to get Na
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tande33
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If its in equilibrium, there will be no resultant force in the vertical or horizontal direction, and there should be no turning effect, so sum of the anti-clockwise moments are equal to the sum of clockwise moments. Hopefully that helps a bit.
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o_reo
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#3
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(Original post by tande33)
If its in equilibrium, there will be no resultant force in the vertical or horizontal direction, and there should be no turning effect, so sum of the anti-clockwise moments are equal to the sum of clockwise moments. Hopefully that helps a bit.
should I take moments about point B?
Even then im not sure how to do that as the forces are all at different angles
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tande33
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(Original post by m.s124)
should I take moments about point B?
Even then im not sure how to do that as the forces are all at different angles
Yes that sounds good, you will need to find the components of the force perpendicular to the ladder, are you familiar with how to do this?
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