Refer to the answer of the question on (1),
Consider the case where the ring is on segment BA:
-Why will the ring slide from B to A when there is no energy lost?
-When the ring is between A and B, is there any tension on S1?
Consider the case where the ring is on segment BC:
-If I altered the question by shifting O to O', where O' is not the center of the circle. The normal force acted on the ring cannot cancel out a component of force of the tension(tangent to the circle). Then shouldn't the ring fall even if the is no lost of potential energy of the hanging mass?
Thank you for answering the questions.
Force and motion problem?
回答 (1)
2016-12-17 8:16 pm
1. When the ring is on segment B to A:
- The hanging mass will fall as the ring is sliding from B to A.
Just consider a position of the ring between B and A, there is a horizontal force, given by S1, pulling the mass towards point A (i.e. towards the right). There is no counter-balance force given by S2 (as S2 will become slack). The mass thus cannot be kept stationary.
- Yes, there is tension on S1.
2. When the ring is on segment B to C:
- It depends on where O' is. But in most cases, an off-centre system is unstable and will collapse. The mass would fall together with the ring.
- The hanging mass will fall as the ring is sliding from B to A.
Just consider a position of the ring between B and A, there is a horizontal force, given by S1, pulling the mass towards point A (i.e. towards the right). There is no counter-balance force given by S2 (as S2 will become slack). The mass thus cannot be kept stationary.
- Yes, there is tension on S1.
2. When the ring is on segment B to C:
- It depends on where O' is. But in most cases, an off-centre system is unstable and will collapse. The mass would fall together with the ring.
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