Understanding Distributed Load Forces: Causes and Effects on Objects

[chetzread]

Homework Statement

why the force of distributed act upward?

Homework Equations

The Attempt at a Solution

why shouldn't it act downward due to gravity pull?

 

[SteamKing]

Homework Statement

why the force of distributed act upward?

Homework Equations

The Attempt at a Solution

why shouldn't it act downward due to gravity pull?

If you read the text in the book, the author has chosen to show the loads acting in their positive direction. which is why F is pointing up rather than down, like a gravity load.

 

[Delta2]

What do you think would change in the equations if you take the load to act downwards?

As long as you keep stable the sign conventions through the whole derivation, nothing changes in the equations.

 

[pongo38]

You may be assuming that the distributed load is against gravity. This problem could be a model of a structural member such as a window mullion carrying a distributed wind load, where gravity is a force along the axis of the member.

 

[chetzread]

You may be assuming that the distributed load is against gravity. This problem could be a model of a structural member such as a window mullion carrying a distributed wind load, where gravity is a force along the axis of the member.

Do you mean the author assume the beam carrying win load , so the forces act upwards?

 

[pongo38]

I don't know what the author assumed. I am just indicating that you have made an assumption that the distributed load is acting vertically, when it might just be acting horizontally if you regard the diagram (a) given as a plan., rather than as an elevation. All this doesn't affect the calculations, but helps you understand a possible application of the mechanics that does occur in everyday engineering practice.