Flag pole finding horizontal force component at hinge.

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SUMMARY

The discussion focuses on calculating the x-component of the force (Fx) exerted by the wall on a flag pole hinged at point A. The flag pole consists of an 80 kg rod and a 10 kg point mass, positioned at a 30-degree angle to the horizontal. The correct x-component of the force is determined to be 850N, achieved by applying the principles of net torque and net force, specifically τ=r x F=Iα. The discussion emphasizes the importance of selecting an appropriate axis for torque calculations to simplify the problem.

PREREQUISITES
  • Understanding of static equilibrium principles (Net torque=0, Net force=0)
  • Familiarity with torque calculations (τ=r x F)
  • Knowledge of moment of inertia (I) and angular acceleration (α)
  • Basic physics concepts related to forces and center of mass
NEXT STEPS
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  • Learn about torque and its applications in rotational dynamics
  • Explore the concept of moment of inertia and its calculation for different shapes
  • Practice problems involving forces on hinged structures and their equilibrium
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Students studying physics, particularly those focusing on mechanics and static equilibrium, as well as educators looking for examples of torque and force calculations in real-world applications.

Parker Hays
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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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