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I am having a difficult time understanding how this works, anyone have any insight?
thank you
Simple machines
- Thread starter monkeyvokes
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I am having a difficult time understanding how this works, anyone have any insight?
thank you
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I remembered this question and was still confused after reading the answer and its explanation. After a while, I figured it out. It's hard to explain with just words, but I'll try.
Pretty much, you have to recognize that the pulley has a pivot that is NOT at the center. Do you see that black dot in the pulley? Basically, the whole point is to recognize that the black dot (pivot) is NOT at the center of the pulley, but it's somewhere off from the center, at the weird spot other than the center.
So let's look at the position 1. And look at the pulley above (or upper pulley) in that arrow, for example. The pivot (black dot) is sort of "far" away from the string that connects the left end of the arrow and touches the pulley (the string right underneath the letter "A"). And look at the same pulley above in that arrow in Position 2. The very same string (the one that connects left end of the arrow and touches or goes around the pulley above, or the string that is right underneath the letter "A") is now "closer" to the black dot (pivot) of the pulley.
Tension is a force, and we know that from torque: the farther you are from the pivot point of the pulley, you can exert less amount of force to bring out the same results or torque.
So the force or tension has to be less in position 1, because the distance between "string" that touches the edge of pulley and "pivot" point (or black dot basically) is longer than the distance in position 2. You have to exert more tension or force on position 2, because the pivot (black dot in the upper pulley) is closer to the string and to make the same torque, you have to exert greater tension to compensate for that "shorter" distance.
I really hope it makes sense. Basically, pay attention to where that black dot is, think of that as a pivot point, and recognize the longer distance in position 1 between string and the pivot that you can have less tension, because of that longer distance so it's "easier" to pull.
Pretty much, you have to recognize that the pulley has a pivot that is NOT at the center. Do you see that black dot in the pulley? Basically, the whole point is to recognize that the black dot (pivot) is NOT at the center of the pulley, but it's somewhere off from the center, at the weird spot other than the center.
So let's look at the position 1. And look at the pulley above (or upper pulley) in that arrow, for example. The pivot (black dot) is sort of "far" away from the string that connects the left end of the arrow and touches the pulley (the string right underneath the letter "A"). And look at the same pulley above in that arrow in Position 2. The very same string (the one that connects left end of the arrow and touches or goes around the pulley above, or the string that is right underneath the letter "A") is now "closer" to the black dot (pivot) of the pulley.
Tension is a force, and we know that from torque: the farther you are from the pivot point of the pulley, you can exert less amount of force to bring out the same results or torque.
So the force or tension has to be less in position 1, because the distance between "string" that touches the edge of pulley and "pivot" point (or black dot basically) is longer than the distance in position 2. You have to exert more tension or force on position 2, because the pivot (black dot in the upper pulley) is closer to the string and to make the same torque, you have to exert greater tension to compensate for that "shorter" distance.
I really hope it makes sense. Basically, pay attention to where that black dot is, think of that as a pivot point, and recognize the longer distance in position 1 between string and the pivot that you can have less tension, because of that longer distance so it's "easier" to pull.
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ohh thank you
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To expand a little bit upon what Lya said, look at the distance of the pulley wheel from the bow. The top pulley wheel in position 2 is closer to that stiff bow than the top pulley wheel in position 1. You need more applied force to move the pulley that's closer to the bow, so the tension yanking back would be greater from where you're tugging on the string in position 2.
Works the same as a lever. The mechanical advantage for all simple machines lies in the trade-off between distance and applied force. The greater the distance you have to apply your force through, the less the force is required to do the same amount of work.
Try to imagine yourself standing there, holding the bow yourself, feeling the tension as you pull back. See if you can feel the bow in your arms, drawing upon your past experiences. It sounds cheesy and flowery, but it can help to intuitively guide you to the solution. 😀
Works the same as a lever. The mechanical advantage for all simple machines lies in the trade-off between distance and applied force. The greater the distance you have to apply your force through, the less the force is required to do the same amount of work.
Try to imagine yourself standing there, holding the bow yourself, feeling the tension as you pull back. See if you can feel the bow in your arms, drawing upon your past experiences. It sounds cheesy and flowery, but it can help to intuitively guide you to the solution. 😀
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