- #1
Why is the reaction force in this direction?
- Thread starter Neon32
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Discussion Overview
The discussion centers around understanding the direction of the reaction force in a mechanical system involving a short cable and a link cable. Participants explore the underlying mechanics rather than relying on memorization, focusing on the theoretical and conceptual aspects of force direction in this context.
Discussion Character
- Exploratory, Technical explanation, Conceptual clarification
Main Points Raised
- One participant seeks to understand the reaction force direction rather than memorize it, indicating a desire for deeper comprehension.
- Another participant suggests considering the resultant forces in other directions to gain insight into the problem.
- A participant explains that from the perspective of the bar, the rope or link is pulling it in a specific direction, while from the rope or link's perspective, the bar is pulling in the opposite direction, using a tug of war analogy.
- It is noted that while a rope can only exert force in its direction, the short link's behavior is influenced by the pins at both ends, which restrict the force transmission direction.
- One participant recommends taking moments about one of the pinned ends to understand the force components and their ratios, which are necessary for achieving a zero resultant moment.
Areas of Agreement / Disagreement
Participants express various viewpoints on the mechanics involved, and while there is some agreement on the importance of analyzing forces from different perspectives, no consensus is reached on a singular explanation for the reaction force direction.
Contextual Notes
Participants discuss the mechanics of force direction without resolving the complexities involved, such as the assumptions related to the system's constraints and the specific definitions of forces at play.
Who May Find This Useful
This discussion may be useful for individuals interested in mechanics, particularly those looking to deepen their understanding of reaction forces in mechanical systems.
- #2
Bystander
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"Why?" Consider the resultant(s) for other directions.
- #3
jack action
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From the point of view of the bar, something (the rope or link) is pulling it in that direction.
If you would analyze it from the rope or link point of view, the bar would be pulling on it and, thus, the direction would be in reverse.
Imagine yourself in tug of war, Who is pulling on the rope? From each team's point of view, it is the other team.
If you would analyze it from the rope or link point of view, the bar would be pulling on it and, thus, the direction would be in reverse.
Imagine yourself in tug of war, Who is pulling on the rope? From each team's point of view, it is the other team.
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- #4
CWatters
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It's easy to understand the case with a rope... It can only provide a force in the same direction as the rope. It's less obvious with the short link but the answer is the pins at the end. Because both ends have pins the link cannot transmit a force in any other direction.
- #5
Randy Beikmann
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Neon32, it should help to take moments about one of the two ends, which are both pinned. The resultant moment must be zero, and that requires a certain ratio of the force components along the coordinate axes (Fx/Fy). That determines the direction of the resultant force.
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