Find the Tension and Acceleration of Cable B in Picture 3

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Homework Help Overview

The discussion revolves around a physics problem involving tension and acceleration in a cable system, specifically focusing on the scenario depicted in picture 3, where one mass (A) has touched the ground and another mass (B) is moving upward. Participants are exploring the implications of these conditions on the tension in the cable and the acceleration of mass B.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants are questioning the nature of tension in the cable at the moment mass A touches the ground, with some suggesting it may be zero based on personal experience. Others are considering how to explain this using physical laws and the behavior of the cable under different conditions.

Discussion Status

The discussion is ongoing, with various interpretations being explored regarding the tension in the cable. Some participants have offered insights into the behavior of the cable when slack and the need to consider forces acting on the masses involved. There is no explicit consensus yet, as participants continue to raise questions and explore different angles of the problem.

Contextual Notes

There is uncertainty regarding the exact moment when mass A touches the ground and how this affects the tension in the cable. Participants note that the cable may not behave as an ideal inextensible cable at that moment, indicating a need for more information about the cable's physical characteristics to fully understand the situation.

arpon
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In picture 3, [itex]A[/itex] has touched the ground, so it has stopped. But [itex]B[/itex] has a velocity upward. So in this situation, the cable is not straight. What will be the tension of the cable and what will be the accelertion of [itex]B[/itex] in picture 3 ? Please explain 'why' in details.
 
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What do YOU think the tension will be in picture 3?
 
Philip Wood said:
What do YOU think the tension will be in picture 3?
I think, it should be 0, from my experience. But, how to explain this by the laws of physics?

I am not sure, what the tension is , just at the moment, when [itex]A[/itex] touches the ground. The cable is straight right at this moment.
 
Cable has no tension when slack. I suppose that, if you wanted laws of Physics, you'd need to look at forces between particles in the rope.
 
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arpon said:
I think, it should be 0, from my experience. But, how to explain this by the laws of physics?
it is zero. You should be able to show this by considering the acceleration (known, for both masses) and the forces on them.

I am not sure, what the tension is , just at the moment, when [itex]A[/itex] touches the ground. The cable is straight right at this moment.
At the exact moment that the cable touches the ground, it won't behave like the idealized perfectly inextensible cable that we've been assuming throughout the problem, so you cannot solve for the tension at that exact moment without knowing a lot more about the detailed physical characteristics of the cable. In problems of this sort, your best bet is to solve for the tension a split second before the weight touches the ground, a split second after, and not worry about what happens during the arbitrarily small time in between.
 
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