The discussion centers on the equilibrium of a uniform beam supported by two bricks when a weight is applied at one end. The key conclusion is that the beam can remain in equilibrium (sum of moments about one brick equals zero) even while tilting, as long as the moments are balanced. This scenario illustrates Newton's first law, which states that an object at rest remains at rest unless acted upon by an external force. The moments can remain balanced during the initial phase of tilting, allowing the beam to start moving at a constant angular velocity.
PREREQUISITESStudents of physics, engineering students, and anyone interested in understanding the principles of static equilibrium and motion dynamics.
Okay, but does the weight on the edge have enough downward force to actually make it tilt or would I need to increase it? If it does have enough downward force to make it tilt then surely it is just a matter of seconds until the beam starts tilting and therefore the sum of moments would not equal 0.Simon Bridge said:In the example, the condition being calculated is for the case that the beam is just about to tilt. The moments exactly balance, so Newtons first law applies.
I see now! Thanks a lot for your help!Simon Bridge said:What does Newton's first law say?
If the beam is stationary, it remains stationary - if it is in motion, it stays in motion - at a constant (angular) velocity.
Lets say it (in the example) is stationary - then, with the moments exactly balanced the slightest extra moment, for the tiniest fraction of a second, will set it in motion at a constant angular velocity. You can see if the moments remain in balance while tilting by redrawing the picture with the beam tilted at some obvious angle, draw in the forces, and calculate the moments. However, they don't have to be out of balance for the beam to keep tilting.