Flag pole finding horizontal force component at hinge.

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To find the x-component of the force exerted by the wall on the flag pole at the hinge, focus on the net torque and net force equations. The center of mass location is less critical; instead, analyze the torque exerted by known forces around a chosen axis, ideally at the hinge. This simplifies calculations, allowing you to avoid unnecessary complexity. The correct answer for the force is 850N, which can be derived by ensuring that both torque and linear force equations are satisfied. Understanding the relationship between these forces and torques is essential for solving the problem accurately.
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Homework Statement


A flag pole consists of a 80 kg rod of length L = 2 m with a 10 kg point mass attached to the end. The pole is hinged at the bottom and is tied to a horizontal cable as shown.
1. What is the x-component of F (Fx) exerted by the wall on the flag pole at the hinged point A?
(The picture shows the flag pole hinged at a 30 degree angle to the horizontal and the 10kg point mass is not on the hinged side).
finImg9.gif

Homework Equations


Net torque=0, Net force=0, τ=r x F=Iα.

The Attempt at a Solution


I've attempted to find the location of the center of mass so that I can know where the gravity acts on the rod. I have gotten many different answers but none of them have been correct. The correct answer is 850N and I don't know how to get there, other than Fnet=0N and τnet=0Nm. I also think torque due to the hinge is zero since it is at the hinge and therefore r x F is zero.
 

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Parker Hays said:
attempted to find the location of the center of mass
That is rarely necessary.
Just consider the torque that each force exerts (about some chosen axis) and sum them.
To choose an axis, look at the forces you do not know and do not need to find. If you can pick an axis on the intersection of their lines of action you will only need the one equation.
Otherwise you will need both torque and linear equations.
 
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