Statics - Show a massless stick feels forces along the stick

AI Thread Summary
A massless stick connected by hinges in a static system experiences forces at the hinges that are directed along its length, ensuring the stick remains stationary. To demonstrate this, one must analyze the force vectors acting on the stick, confirming that they must align to prevent movement or rotation. When a mass is added to the stick, the forces can no longer be constrained to point along the stick due to the influence of gravity, allowing for a more complex interaction of forces. The key to understanding these dynamics lies in recognizing that static equilibrium requires a balance of forces and moments. Overall, the analysis of force direction is critical in both scenarios to maintain the stick's static condition.
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Homework Statement


A stick is connected to other partrs of a static system by hinges at its ends. Show that a massless stick feels forces, at the hinges, that are directed along the stick. Then show if the stick is massive, the forces do not need to point along the stick.


Homework Equations





The Attempt at a Solution


I have no idea where to start or how I can write this out to prove it in every situation. For instance its obvious the the stick attached to a wall and then a block, with a force point away from the wall, that all the forces go with the stick (exactly like tension in a massless rope). Then when mass is introduced the force of gravity clearly offsets the forces felt. I can use the later for the second part, but how does one go about showing the first part in all situations?
 
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The key is that the system, including the stick, is static - i.e. the stick does not move.

So, draw a stick in space, and draw a couple of random force vectors at each end. What do the forces have to do for the stick to not move? It's not allowed to rotate or translate.

If the forces don't point directly down the stick, how can they balance?
 
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