## Simple Machines B/Compound Machines C

JonB
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### Re: Simple Machines B/Compound Machines C

Unome wrote:How does efficiency in pulleys work anyway? My logic (which may not make sense since the system is stable) was that as the rope is pulled through the pulley, it loses 10% of its tension, so the right side ropes need more tension than the left side.

I can best explain this with an example:

In the following image, the left pulley is assumed to be 100% efficient and the right pulley 1% efficient (some arbitrary number showing great inefficiency)
You can clearly see that the left pulley would only remain stationary if the two masses are equal; this isn't the case with the right pulley. For example, if the source of the right pulley's inefficiency was rust (illustrated rather horribly in Paint), then it is reasonable to assume that the right pulley could remain stable as shown, with unequal masses on either side.
That is the basis for my reasoning that pulley inefficiency does carry over into the stationary case.
paintshop.png (6.08 KiB) Viewed 2320 times

Unome
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### Re: Simple Machines B/Compound Machines C

JonB wrote:
Unome wrote:How does efficiency in pulleys work anyway? My logic (which may not make sense since the system is stable) was that as the rope is pulled through the pulley, it loses 10% of its tension, so the right side ropes need more tension than the left side.

I can best explain this with an example:

In the following image, the left pulley is assumed to be 100% efficient and the right pulley 1% efficient (some arbitrary number showing great inefficiency)
You can clearly see that the left pulley would only remain stationary if the two masses are equal; this isn't the case with the right pulley. For example, if the source of the right pulley's inefficiency was rust (illustrated rather horribly in Paint), then it is reasonable to assume that the right pulley could remain stable as shown, with unequal masses on either side.
That is the basis for my reasoning that pulley inefficiency does carry over into the stationary case.
paintshop.png

Ok... I sort of get it. Anyway, the first person that gets here can ask a question.
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### Re: Simple Machines B/Compound Machines C

Unome wrote:
JonB wrote:
Unome wrote:How does efficiency in pulleys work anyway? My logic (which may not make sense since the system is stable) was that as the rope is pulled through the pulley, it loses 10% of its tension, so the right side ropes need more tension than the left side.

I can best explain this with an example:

In the following image, the left pulley is assumed to be 100% efficient and the right pulley 1% efficient (some arbitrary number showing great inefficiency)
You can clearly see that the left pulley would only remain stationary if the two masses are equal; this isn't the case with the right pulley. For example, if the source of the right pulley's inefficiency was rust (illustrated rather horribly in Paint), then it is reasonable to assume that the right pulley could remain stable as shown, with unequal masses on either side.
That is the basis for my reasoning that pulley inefficiency does carry over into the stationary case.
paintshop.png

Ok... I sort of get it. Anyway, the first person that gets here can ask a question.

Extremely simple question:
What is the "law of the lever?"

jkang
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### Re: Simple Machines B/Compound Machines C

UTF-8 U+6211 U+662F wrote:What is the "law of the lever?"

d1F1 = d2F2, where d = distance from the fulcrum and F = force applied
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### Re: Simple Machines B/Compound Machines C

jkang wrote:
UTF-8 U+6211 U+662F wrote:What is the "law of the lever?"

d1F1 = d2F2, where d = distance from the fulcrum and F = force applied

jkang
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### Re: Simple Machines B/Compound Machines C

Another pretty simple question: Identify all of the simple machines in a nail clipper (include different classes of levers, if applicable).
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mjcox2000
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### Re: Simple Machines B/Compound Machines C

2 wedges, 1 second class lever, 2 third class levers. (That dotted line is a pin connected to the bottom 3rd class lever, going through the top one, and connected to the 2nd class lever.) There's a spring keeping the two 3rd class levers apart - that isn't a simple machine, but it's part of the resistance, so I thought I'd mention it. Effort is applied at the long end of the 2nd class lever and the vertex of the two 3rd class levers.
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jkang
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### Re: Simple Machines B/Compound Machines C

mjcox2000 wrote:
Nail clipper diagram.jpg

2 wedges, 1 second class lever, 2 third class levers. (That dotted line is a pin connected to the bottom 3rd class lever, going through the top one, and connected to the 2nd class lever.) There's a spring keeping the two 3rd class levers apart - that isn't a simple machine, but it's part of the resistance, so I thought I'd mention it. Effort is applied at the long end of the 2nd class lever and the vertex of the two 3rd class levers.

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mjcox2000
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### Re: Simple Machines B/Compound Machines C

How do actual mechanical advantage and ideal mechanical advantage differ? When would one want to know IMA instead of AMA, and vice versa? (This wasn't original - it was on our state test - but I thought it was not a bad question.)
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### Re: Simple Machines B/Compound Machines C

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### Re: Simple Machines B/Compound Machines C

finagle29 wrote:

That sounds right to me, you should go ahead and ask the next question.
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### Re: Simple Machines B/Compound Machines C

How are a machine's Q-factor and efficiency related, and how do these relate to whether or not it is self-locking? Additionally, for each type of simple machine, state whether or not, in its normal mode of use, it would be advantageous for it to be self-locking.
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jkang
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### Re: Simple Machines B/Compound Machines C

finagle29 wrote:How are a machine's Q-factor and efficiency related, and how do these relate to whether or not it is self-locking? Additionally, for each type of simple machine, state whether or not, in its normal mode of use, it would be advantageous for it to be self-locking.

Not completely sure but...
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### Re: Simple Machines B/Compound Machines C

JonB wrote:
Unome wrote:How does efficiency in pulleys work anyway? My logic (which may not make sense since the system is stable) was that as the rope is pulled through the pulley, it loses 10% of its tension, so the right side ropes need more tension than the left side.

I can best explain this with an example:

In the following image, the left pulley is assumed to be 100% efficient and the right pulley 1% efficient (some arbitrary number showing great inefficiency)
You can clearly see that the left pulley would only remain stationary if the two masses are equal; this isn't the case with the right pulley. For example, if the source of the right pulley's inefficiency was rust (illustrated rather horribly in Paint), then it is reasonable to assume that the right pulley could remain stable as shown, with unequal masses on either side.
That is the basis for my reasoning that pulley inefficiency does carry over into the stationary case.
paintshop.png

but aren't pulleys symmetrical? Therefore, you could flip the image and get an efficiency of ~111%.

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### Re: Simple Machines B/Compound Machines C

This one's easy. Suppose you are dropping an anvil that weighs 8.7 kg 1.864 km straight down. Calculate the work done.