- #1
binbagsss
- 1,265
- 11
The direction of rotating bodies about a fixed axis.
I am confused on how you should regard the the direction of mg sin x, the angular acceleration and the force exerted on the body by the axis, perpendicular to OG ( where O is the fixed axis location and G is the centre of mass of the body).
There are key scenarios in that a rotating body could be at the bottom of its circular motion.
I have attached diagrams indicating both, and have labelled on a direction of angular speed.
Okay so in diagram 1, where the mass is APPROACHING the lowest point, it is speeding up. Taking downward as negative then , I would conclude:
- mg sin x : negative
- Y (force exerted by axis) : positive - you can go either way?
- Angular acceleration, most importantly, I would take this as negative - my reasoning being that the body is moving downward at this point whilst increasing in speed.
In diagram 2 I would conculde:
- mg sin x : negative
- Y (force exerted by axis) : positive - you can go either way?
- Angular acceleration, most importantly, I would take this as negative - my reasoning being that the body is moving upward at this point whilst decreasing in speed.
I asuume that I must be regarding the angular acceleration incorrectly to reach the same conclusion in both cases ! Any assistance, really, really appreciated, thaks a lot ! =]
I am confused on how you should regard the the direction of mg sin x, the angular acceleration and the force exerted on the body by the axis, perpendicular to OG ( where O is the fixed axis location and G is the centre of mass of the body).
There are key scenarios in that a rotating body could be at the bottom of its circular motion.
I have attached diagrams indicating both, and have labelled on a direction of angular speed.
Okay so in diagram 1, where the mass is APPROACHING the lowest point, it is speeding up. Taking downward as negative then , I would conclude:
- mg sin x : negative
- Y (force exerted by axis) : positive - you can go either way?
- Angular acceleration, most importantly, I would take this as negative - my reasoning being that the body is moving downward at this point whilst increasing in speed.
In diagram 2 I would conculde:
- mg sin x : negative
- Y (force exerted by axis) : positive - you can go either way?
- Angular acceleration, most importantly, I would take this as negative - my reasoning being that the body is moving upward at this point whilst decreasing in speed.
I asuume that I must be regarding the angular acceleration incorrectly to reach the same conclusion in both cases ! Any assistance, really, really appreciated, thaks a lot ! =]