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1. 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.
2. (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.
3. (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.
4. (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.
5. (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)
6. (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 at A is 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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