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    A ladder AB, length 3.6m and, mass 15kg, is in equilibrium resting against a smooth vertical wall. A is inclined at 40' on top of a rough horizontal block, B rests against the wall.

    Find the normal reaction and friction at A. Hence show that coeff of friction is greater than 0.596.

    Thanks for any help.
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    (Original post by Anonsfk)
    A ladder AB, length 3.6m and, mass 15kg, is in equilibrium resting against a smooth vertical wall. A is inclined at 40' on top of a rough horizontal block, B rests against the wall.

    Find the normal reaction and friction at A. Hence show that coeff of friction is greater than 0.596.

    Thanks for any help.
    Draw a diagram to model the situation first, labeling all forces.
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    (Original post by RDKGames)
    Draw a diagram to model the situation first, labeling all forces.
    I tried to do that and have taken moments and resolved and I am unable to get what i need to.
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    (Original post by Anonsfk)
    I tried to do that and have taken moments and resolved and I am unable to get what i need to.
    Sounds like the correct approach. Let's see exactly what you've done then to determine where it goes wrong.
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    (Original post by RDKGames)
    Sounds like the correct approach. Let's see exactly what you've done then to determine where it goes wrong.
    1. I took moments about a for AB
    - This meant that I found the Reaction force at B as 56.304...
    2. Resolved horizontally
    - Therefore friction =Rbsin40= 36.1916...
    3. Resolve vertically
    - Therefore Reaction at A= 103.868..

    Therefore coeff of friction= Fr/Ra but it doesn't...
    (I know I have probably made an obvious mistake, sorry in advance)
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    (Original post by Anonsfk)
    1. I took moments about a for AB
    - This meant that I found the Reaction force at B as 56.304...
    This is not entirely correct. Check this.

    2. Resolved horizontally
    - Therefore friction =Rbsin40= 36.1916...
    If you are going to resolve horizontally, then you need to state that the frictional force is \mu R at A is \geq than the only other force going in the opposite direction, that is the reaction force at B.

    3. Resolve vertically
    - Therefore Reaction at A= 103.868..
    Again, not sure where this comes from. Resolving vertically you must have the reaction force at A equal to the only other force going down which is the weight.
 
 
 
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