Torque- rigid objects in equalibrium/ center of gravity.

AI Thread Summary
The discussion focuses on calculating the forces acting on a uniform door hung on two hinges, with specific attention to torque and equilibrium. The door weighs 140N, and the lower hinge is assumed to bear all its weight, while the upper hinge's horizontal force component needs to be determined. Participants emphasize the importance of selecting the correct pivot point, which is suggested to be the lower hinge, to analyze the torque effectively. The conversation also highlights the need to consider the door's center of gravity and the resulting torque about the hinges. Overall, the thread seeks guidance on applying torque equations to solve the problem accurately.
utnip123
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Homework Statement


A uniform door(.81m wide and 2.1m high) weighs 140N and is hung on two hinges that fasten the long left side of the door to a vertical wall. The hinges are 2.1m apart. Assume that the lower hinge bears all the weight of the door. Find the magnitude and direction of the horizontal component of the force applied to the door by a) the upper hinge and the lower hinge. Determine the magnitude and direction of the force applied by the door to b) the upper hinge and the lower hinge.

Fg = 140 N

Homework Equations


ƩT = F L
am stuck on how the torque equation applies to this problem

The Attempt at a Solution


i drew the diagram of the door and the hinges spaced 2.01 m apart.
I think you have to make the pivot point/axle point at the bottom hinge

sum of the verticle forces = weight of the door, I am assuming this.
Am not sure how to even begin this question. but do i start to make x components at the hinges?

any advice would be helpfull.

thanks
 
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utnip123 said:

Homework Statement


A uniform door(.81m wide and 2.1m high) weighs 140N and is hung on two hinges that fasten the long left side of the door to a vertical wall. The hinges are 2.1m apart. Assume that the lower hinge bears all the weight of the door. Find the magnitude and direction of the horizontal component of the force applied to the door by a) the upper hinge and the lower hinge. Determine the magnitude and direction of the force applied by the door to b) the upper hinge and the lower hinge.

Fg = 140 N

Homework Equations


ƩT = F L
am stuck on how the torque equation applies to this problem


The Attempt at a Solution


i drew the diagram of the door and the hinges spaced 2.01 m apart.
I think you have to make the pivot point/axle point at the bottom hinge

sum of the verticle forces = weight of the door, I am assuming this.
Am not sure how to even begin this question. but do i start to make x components at the hinges?

any advice would be helpfull.

thanks
Hello utnip. Welcome to PF !

Assume that gravity acts downward on the door at its center. That will produce a torque about the hinges. Find the torque about the lower hinge.
 
See image below
 

Attachments

but where is your axis on the door?
 
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