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QUESTION: I have some doubt about Law of conservation of Energy.This law says that energy cannot be created or destroyed,but by giving some examples & when i compare some formulas ,i can see that energy can be created

Example 1. we know about screw jack ,it is used to lift heavy loads & objects. It is a device that increases the magnitude of force.For a screw jack
F = (w*p)/2(3.14)R
where F=force,W=weight,P=pitch of screw,R=length of lever
now ,if W=100000 lb,P=0.125 inch,R=18 inch then after calculation F=110.58033 lb. 1 pound=4.4482216 newton so from this
F=491.88581 newton. This means that to lift a weight of 100000 lb i need to apply a force of 491.88581 newton. Above example shows that this screw jack increases force nearly upto 1000 times so ratio is nearly 1:1000

Example 2. work=Force*Distance also Energy=Force*Distance
suppose i push an object from point A to point B
Distance between A&B is 1 meter ,force applied by me is 1000 newton so work=1000*1= 1000 newton-meter or joule
It means, for doing this given work 1000 joule energy is required

Now suppose for doing this same work i use the screw jack that increases the force up to 1000 times(1:1000)as given in example 1.
with the help of screw jack (keeping horizontally)i will push the object,but as the screw jack increases the force up to 1000 times i need to apply only 1 newton force so this time
work=1*1=1 newton-meter or joule so this time for doing the same work i required only 1 joule energy to apply

Question:- by comparing above examples & works, can i say that while doing above work with the help of screw jack , energy is created ?

ANSWER: Not even close, sorry.  You're talking about applied Newtons and distances as if there were no accelerations involved.  If you apply constant force and no speed changes (changing kinetic energy) then you have to apply an equal and opposite force to stop the change in velocity.  I started applying examples, but basically it comes down to this:  You're not applying the force on the screw, you're applying the force around the screw.  The screw is still applying the same force, but the distance you have to travel around the screw according to your formula is 1000 times as far if you get a pure (frictionless) mechanical advantage according to your numbers.  It works out that energy is still conserved.  

---------- FOLLOW-UP ----------

QUESTION: thanks for replying
I think you will atleast agree that screw jack makes impossible things possible.As ,it is impossible to lift 100000 lb weight but using screw jack by applying just 491.88581 newton of force it can be lift or push easily.

It was a limited work because normally screw jack has a short length screw so it can be raised or pushed upto limited height/distance in one direction
But there are some possibilities

suppose we have an imaginary screw jack with endless screw OR

circular screw (screw in a circle shape which is made of strong but flexible material OR

A screw jack with a system that insert or provide a screw continuously from bottom side of jack.

Then such screw jack can work continuously by rotating in one direction (clockwise) with no limit.
If we use such screw jack then there will be continuous energy flow
My idea was to use such jack in electricity generation
In power stations ,generally energy is applied to turbine ,mechanical energy of turbine then rotates the generator & electrical energy is generated
My basic idea is to use the jack (with rotating screw)before the turbine in electricity generation process
I mean that we apply the particular form of energy first to the screw jack (with rotating screw),further to turbine and so on.
I think that if we do so we will get efficiency more than 100% or atleast 100%
I say this because i have a thinking that applying less effort extreme heavy weights can be lift easily by screw jack but it has a limit as i talk before
But rather than using screw jack only for lifting purpose if we convert/modify a screw jack in a way as i say above
Then similarly by applying less/low effort through such modified screw jack ,big heavy generators can be rotated easily for generating electricity. It means input is less but output is very high

Question :Do you agree with my thinking ? By this way in the form of electricity ,energy can be created or not?

Answer
You're forgetting the thing I mentioned.  It's not about just the distance that the screw applies the force over.  In order to move it, your hand must move around and around on the lever a distance far greater than the screw head moves.  More than enough to account for the energy output of the screw, because the force on your hand * the distance it must go through is now a greater quantity of energy than you can recover from the higher force * shorter distance.  In the end, the screw jack is a complex lever.  Multiply force input to output, yes it can do that.  Add energy?  No, energy does not just come from nothing and your must move the input end too far to get extra energy from the output end.  It doesn't work any other way, no matter how much we wish it did.

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Dr. Stephen O. Nelson

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I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

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I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

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Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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