Solving Equilibrium: 80N Ladder on Wall & Ground

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Homework Help Overview

The problem involves a ladder of weight 80N resting against a smooth wall at a 29-degree angle to the vertical, with its base on a rough horizontal floor. The discussion centers around calculating the reaction forces at the ground and wall when the ladder is in equilibrium, as well as determining the coefficient of friction required to prevent slipping when a man of equal weight climbs to the top.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the equilibrium conditions, noting the need for multiple equations due to the presence of four unknowns. There is an exploration of the forces acting on the ladder, including vertical and horizontal components, and the implications of the wall being smooth. Some participants question the correctness of calculated forces and seek clarification on the laws of motion involved.

Discussion Status

The discussion is ongoing, with participants sharing their calculations and questioning their accuracy. Some guidance has been offered regarding the need for additional equations to solve for the unknowns, particularly through the sum of moments. There is no explicit consensus on the correctness of the calculations presented.

Contextual Notes

Participants note the absence of specific information regarding the length of the ladder and the coefficient of friction, which may affect the calculations and assumptions being made.

IBB
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Homework Statement


A)A ladder of weight 80N rests against a smooth wall at an angle of 29 degrees to the vertical with its end on a rough horizontal floor.If the ladder is in equillibrium calculate the reaction (magnitude and direction) of the ground and the wall.
Bi)a man of weight 80N climbs to the top,determine the force reaction of the ground and the wall
Bii)What is the minimum value for μ the coefficient of friction if the ladder does not slip.
All the examples i look at involve a length for the ladder and a figure for μ.

Homework Equations


the sum of all the forces in the x direction are equal to zero and likewise in the y direction.

The Attempt at a Solution


I would have thought that it would just be a opposing the weight of the ladder so reaction at the floor would just be 80N in a upward direction and the reaction of the wall would be the force of friction μ to the right.
 
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The two end points of the ladder both have a reaction force in x and y direction, so you have 4 unknowns. The problem states that the wall is smooth, so the vertical force at the top point of the ladder is Fy=0. You still need another equation.
2. The sum of the moments is zero. The sum of the moments around the point where the ladder touches the floor will give you another equation.
 
thanks for your reply,i have calculated the vertical forces to be equal to 80/Cos29=91.47N
Horizontal 91.47*Sin29=44.35N
Do you know whether these are correct?
In regards to the equation are they Newtons second and third laws?
 
IBB said:
i have calculated the vertical forces to be equal to 80/Cos29=91.47N
Horizontal 91.47*Sin29=44.35N
Do you know whether these are correct?
No, they're not. Please post your working.
 

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