## Simple Machines B/Compound Machines C

Eggo
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### Simple Machines B/Compound Machines C

Welcome to the Marathon for Simple Machines and Compound Machines!
Note: (I thought I might as well start a question marathon for Simple Machines and Compound Machines since no one else did. )
Lets start off with: What class of a lever is the human forearm and why?
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bernard
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### Re: Simple Machines B/Compound Machines C

A human forearm is a [b]Class 3[/b] lever because the load and effort are on the same side of the fulcrum, with the load farther from the fulcrum. Here are some diagrams that illustrate this: [url=http://leo.koppel.ca/backhoe/levers.png]diagram of levers[/url] and [url=http://sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/sporting_edge/sci_media/bent_arm/14731-3-eng-NZ/bent_arm_full_size_landscape.jpg]diagram of arm[/url].
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Eggo
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### Re: Simple Machines B/Compound Machines C

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

A pulley has an AMA of 4, it is used to lift up a 100 N block. How much force will someone have to exert to lift it.

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

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

25N
Unome, your answer seems correct to me. Since the asker has not been on for a few days, feel free to go ahead and ask the next question.

$AMA = \frac{F_{out}}{F_{in}} \to 4 = \frac{100 \hspace{1} N}{F_{in}} \to F_{in} = 25 \hspace{1} N$
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### Re: Simple Machines B/Compound Machines C

A 1st class lever exists with three weights. One side contains a 4.0 kilogram weight at 0.600 meters from the fulcrum, and a weight with a mass of K at 1.3 meters from the fulcrum. The other side has a 7.0 kilogram weight with a volume of 700. centimeters cubed immersed in water, at a distance of 1.0 meters from the fulcrum. Find K (Rounded to sigfigs)
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ageek
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### Re: Simple Machines B/Compound Machines C

I'm not exactly sure what the "immersed in water" or the volume has on the effect, except that I can assume that it's balanced (I hope)
If the kg*m is the same on either side, 7.0kg*1.0m-4.0kg*0.6m=4.6kg*m,4.6kg*m/1.3m~=3.538kg

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

A 1st class lever exists with three weights. One side contains a 4.0 kilogram weight at 0.600 meters from the fulcrum, and a weight with a mass of K at 1.3 meters from the fulcrum. The other side has a 7.0 kilogram weight with a volume of 700. centimeters cubed immersed in water, at a distance of 1.0 meters from the fulcrum. Find K (Rounded to sigfigs)
K = 3.0 kg
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