The discussion revolves around the equilibrium of a uniform beam supported by bricks when a weight is attached at one end, leading to a tilting scenario. Participants explore the conditions under which the beam can be considered in equilibrium despite the tilting motion, focusing on concepts from mechanics, particularly Newton's laws and the balance of moments.
Participants exhibit some agreement on the application of Newton's first law and the conditions for equilibrium, but there remains uncertainty regarding the implications of the weight's force and the transition from equilibrium to motion. The discussion does not reach a consensus on the necessity of additional weight for tilting to occur.
Participants discuss the nuances of moments and forces in the context of tilting, but there are unresolved assumptions about the specific conditions under which the beam transitions from equilibrium to motion. The discussion does not clarify the exact thresholds for these transitions.
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.