Mechanics maths help

so there is one thing that I don't understand about moments in mechanics

say if there is a seesaw and the (not light) plank is at equilibrium on top of the pivot.
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would the plank exert a normal reaction or would the pivot exert a normal reaction????

The COM must be over the pivot, so the pivot will exert an opposite reaction on the plank.
* Taking moments about the pivot is zero everywhere.as the only forces are at the point where you're taking moments.
* Taking moments about either end will mean the moments due to COM and pivot reaction are equal and opposite and hence cancel.
In all cases, its in equilibrium.

i THINK the plank would exert a normal reaction, but im not sure. Is there a specific question you need help with or is this a general question?

what is a COM??? lol I don't understand

what is a COM??? lol I don't understand



yep its a general question....

why do you think that the plank would exert the normal force??? I just don't understand

COM - center of mass.
Gravity pulls the plank down, acting through the COM. The pivot exerts an equal and opposite reaction force on the plank.

this is what I understand so far ... please tell me if im correct

so the plank weighs down on the pivot

the pivot will then exert an equal and opposite force onto the plank

COM - center of mass.
Gravity pulls the plank down, acting through the COM. The pivot exerts an equal and opposite reaction force on the plank.

this is what I understand so far ... please tell me if im correct

so the plank weighs down on the pivot

the pivot will then exert an equal and opposite force onto the plank