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Static Equilibrium

DanielDaniels

Which is in static Equilibrium? provided that none is pivoted.

statc.PNG4.2KB

Reply 1

Stonebridge

Original post by Daniel Atieh

Which is in static Equilibrium? provided that none is pivoted.

Tell us what YOU think and WHY.

Reply 2

DanielDaniels

Original post by Stonebridge

Tell us what YOU think and WHY.

Correct.

My guess would be the first one, since we are not having a pivot point, the object will be treated with no turning effect. So, in the first one, sigma F = 0

Reply 3

Stonebridge

Correct.

The first will be in static equilibrium.
The 2nd will initially rotate and the 3rd will move to the right.

Reply 4

DanielDaniels

Original post by Stonebridge

Correct.

The first will be in static equilibrium.
The 2nd will initially rotate and the 3rd will move to the right.

Thanks a bunch!

The situation would be different if it was pivoted right?

Reply 5

Stonebridge

Original post by Daniel Atieh

Thanks a bunch!

The situation would be different if it was pivoted right?

Yes in principle but exactly what happens would depend where you put the pivot.
The pivot introduces another force so each situation would be different.

Reply 6

DanielDaniels

Original post by Stonebridge

Yes in principle but exactly what happens would depend where you put the pivot.
The pivot introduces another force so each situation would be different.

Thank you.

So for the first image, sum of Forces and Torques = 0 right?
I can show that sum of T is 0 if i take the center of mass as the point of rotation?

Reply 7

Stonebridge

Original post by Daniel Atieh

Thank you.

So for the first image, sum of Forces and Torques = 0 right?
I can show that sum of T is 0 if i take the center of mass as the point of rotation?

You could but how do you know where the centre of mass is?
Are you told these are uniform spheres or disks?

You can argue using symmetry, which is always powerful.
So long as the three forces are parallel and the one acting downwards acts exactly half way between the two acting upwards, then it actually doesn't matter where you take as the point of rotation, or, more correctly, the point about which you measure the torques.
Try it.