Understanding Normal Force Direction in Leaning Ladder & Cable Beam Systems

In summary: From the picture above, the normal force is normal to the wall. If the beam is not attached to the wall, then it will fall down due to the frictional force.
  • #1
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I know that normal force is a reaction force.

http://www.sumoware.com/images/temp/xzhhpaacgkdktjna.png [Broken]
In the leaning ladder problem, the normal force is perpendicular to the floor and the wall.
But, in the cable and beam problem, why isn't the normal force perpendicular to the wall ?

http://www.sumoware.com/images/temp/xzeanhxxmcalmnkn.png [Broken] Hmm.. Then, I imagine what the system (cable and beam) will be without the wall.
I think that the beam will fall down.
And, because the beam touches the wall, the wall will exert a force back to the beam at right direction.
So, the normal force will have up and right direction.

But, I imagine the ladder problem.
But, Why the N1 doesn't have the upward direction ?
I think if there is no wall, then the ladder must fall and rotate counter-clockwise.

Please explain me how to determine the normal force direction.
 
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  • #2
A normal force is by definition normal to the surface. If there is nothing else holding the beam at its contact point, it will fall down. The "something else" can be a frictional force due to a rough surface (in which case the resultant force will not be normal to the wall) or that the beam has been attached to the wall.
 
  • #3
Orodruin said:
A normal force is by definition normal to the surface. If there is nothing else holding the beam at its contact point, it will fall down. The "something else" can be a frictional force due to a rough surface (in which case the resultant force will not be normal to the wall) or that the beam has been attached to the wall.

Hmm..
So, the force in up direction on the hinge is the frictional force
And the force in right direction on the hinge is the normal force
The resultant is the frictonal force + the normal force
Do I get this right?

And, if the beam is attached to the wall, is there any normal force ?
 
  • #4
terryds said:
So, the force in up direction on the hinge is the frictional force

If you have a hinge, it is a completely different situation. There is a normal force from the hinge, but the hinge contact point is not tilted in the same direction as the wall. It is therefore misleading to talk about it as a normal force to the wall.
 
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  • #5
Orodruin said:
If you have a hinge, it is a completely different situation. There is a normal force from the hinge, but the hinge contact point is not tilted in the same direction as the wall. It is therefore misleading to talk about it as a normal force to the wall.

image100820141719.jpg

From the picture above, I have no idea about 'not tilted in the same direction as the wall'.
Then, how to know that the normal force is up and right in direction ?
What will the condition be if the normal force is down and right, or down and left, or etc ?
 
  • #6
You do not, you can guess it (based on the other forces present) and define your force components in such a way, but you will not know for sure until you do the equilibrium analysis and find out what the components of the force are. The condition is that the beam is in equilibrium and the rest should follow from there.
 

What is normal force?

The normal force is the force exerted by a surface on an object that is in contact with it. It is always perpendicular to the surface and prevents the object from passing through the surface.

How does normal force relate to leaning ladder and cable beam systems?

In a leaning ladder or cable beam system, the normal force is the force that supports the weight of the object and keeps it in equilibrium. It is directed perpendicular to the surface of the ladder or beam and prevents the object from falling.

What factors affect the direction of normal force in these systems?

The direction of normal force in leaning ladder and cable beam systems is affected by the angle of the ladder or beam, the weight and distribution of the object, and the strength and stability of the support surface.

How can I calculate the direction and magnitude of normal force in these systems?

To calculate the direction and magnitude of normal force, you can use the equations of equilibrium to balance the forces acting on the object. The normal force will be equal and opposite to the weight of the object, and its direction can be determined using trigonometric functions.

What are some practical applications of understanding normal force direction in these systems?

Understanding the direction of normal force in leaning ladder and cable beam systems is important for ensuring the safety and stability of structures such as bridges, cranes, and scaffolding. It also helps in designing and constructing these structures to withstand the forces acting on them.

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