Simple Machines B/Compound Machines C

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Simple Machines B/Compound Machines C

Postby Eggo » November 11th, 2014, 9:47 am

Welcome to the Marathon for Simple Machines and Compound Machines!
Remember to hide your answers!
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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Re: Simple Machines B/Compound Machines C

Postby bernard » November 11th, 2014, 10:18 am

Answer
A human forearm is a Class 3 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: diagram of levers and diagram of arm.
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Re: Simple Machines B/Compound Machines C

Postby Eggo » November 14th, 2014, 11:18 am

Correct! Your turn!
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Re: Simple Machines B/Compound Machines C

Postby XturtleX » November 19th, 2014, 4:38 pm

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

Postby Unome » November 19th, 2014, 6:00 pm

Answer
25N
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Re: Simple Machines B/Compound Machines C

Postby bernard » November 23rd, 2014, 2:29 pm

Unome wrote:
Answer
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.

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Re: Simple Machines B/Compound Machines C

Postby Unome » November 23rd, 2014, 2:51 pm

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

Postby ageek » December 2nd, 2014, 3:25 pm

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)
But here is my answer according to those assumptions
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

Postby chinesesushi » December 2nd, 2014, 4:50 pm

Unome wrote::twisted:
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)


Answer??
K = 3.0 kg
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Re: Simple Machines B/Compound Machines C

Postby Unome » December 3rd, 2014, 4:16 am

Correct! Your turn. :D
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Re: Simple Machines B/Compound Machines C

Postby chinesesushi » December 3rd, 2014, 8:13 am

Unome wrote:Correct! Your turn. :D

who's correct?
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Re: Simple Machines B/Compound Machines C

Postby chinesesushi » December 3rd, 2014, 11:35 am

Unome wrote:Correct! Your turn. :D


What is the mechanical advantage of each of the pulleys. https://www.lhup.edu/~dsimanek/scenario ... ulley1.gif

If f = 10 N and L has a mass of 3 kg what is the AMA. What is the efficiency.
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Re: Simple Machines B/Compound Machines C

Postby Unome » December 3rd, 2014, 1:18 pm

chinesesushi wrote:
Unome wrote:Correct! Your turn. :D


What is the mechanical advantage of each of the pulleys. https://www.lhup.edu/~dsimanek/scenario ... ulley1.gif

If f = 10 N and L has a mass of 3 kg what is the AMA. What is the efficiency.

Sorry, yes you were the correct one (Unfortunately, I can't also answer the question because the page won't load (it's a problem on my side not, with the image))
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Re: Simple Machines B/Compound Machines C

Postby mjcox2000 » December 3rd, 2014, 5:45 pm

chinesesushi wrote:
Unome wrote:Correct! Your turn. :D


What is the mechanical advantage of each of the pulleys. https://www.lhup.edu/~dsimanek/scenario ... ulley1.gif

If f = 10 N and L has a mass of 3 kg what is the AMA. What is the efficiency.

A) IMA=4, AMA=3, efficiency=75% (80% with sig figs)
B) IMA=32, AMA=3, efficiency=9.375% (10% with sig figs)
C) IMA=3, AMA=3, efficiency=100%
(these are assuming the gravitational constant is rounded to 10, because otherwise C's efficiency is above 100%)
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Re: Simple Machines B/Compound Machines C

Postby chinesesushi » December 3rd, 2014, 6:12 pm

a is right.
b is right.
c is wrong (btw why can't it be 9.8. AMA = 9.8*3/10 = 2.94. efficiency = AMA / IMA = 2.94 / 3 < 1)
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