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connerdom
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#1
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#1
can some one explan the process behind conversion of energy so for example
a ball falls 3.2 meters to the ground. using energy consevation only what is its final speed as it hits the surface.

we have been told to do it like this but i dont understand it
Loss of GPE = Gain in KE
mg^h = 1/2m(v*v)

KEY ^=Delta
(v*v) = squared
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Joinedup
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I can't really see what you're stuck on tbh...

are you happy that the ball has velocity at the instant it first begins to touch the floor and hasn't started to compress yet?
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pipyat
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(Original post by connerdom)
can some one explan the process behind conversion of energy so for example
a ball falls 3.2 meters to the ground. using energy consevation only what is its final speed as it hits the surface.

we have been told to do it like this but i dont understand it
Loss of GPE = Gain in KE
mg^h = 1/2m(v*v)

KEY ^=Delta
(v*v) = squared
Hi there. The gravitational potential energy will be converted into kinetic energy as it falls so you can make use of mgh = 1/2mv^2. Remember energy is never lost, its just transferred therefore the energy the ball has due to its position in the earth's gravitional field (height) will be used up as the ball falls. In this case the M's cancel out leaving you with gh = 1/2v^2. You can rearrange this equation to get v and subsititue in the correct values. I hope that helps.
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Phichi
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(Original post by Ifailedumad)
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I've had a quick read of this and I highly suggest that you do some reading on this topic as most of what you've stated here is inaccurate! Unfortunately I think this will only confuse the OP more so
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Username4647
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(Original post by Phichi)
I've had a quick read of this and I highly suggest that you do some reading on this topic as most of what you've stated here is inaccurate! Unfortunately I think this will only confuse the OP more so
Ah sorry. Would I be wrong in assuming that the work done by gravity on the ball is the gain in kinetic energy on the ball because no other force acts on it? now I am confused, nyway deleted that post
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Phichi
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(Original post by Ifailedumad)
Ah sorry. Would I be wrong in assuming that the work done by gravity on the ball is the gain in kinetic energy on the ball because no other force acts on it? now I am confused, nyway deleted that post
Your conclusion that the change in GPE of the object is equal to the change in KE is correct, however the rest of it was quite incorrect, I could see the intention but it confused even me and I'm doing a physics degree!
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Username4647
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just in response to the post above ^ with no intention of hijacking this thread i just need someone to clarify, because i seem to have some tragically misguided/wrong ideas.

- I defined energy as : that which is transferred when a force is applied over a distance. I also said we dont fundamentally know what it is. but now looking back at the definition, energy is the ability to work. and work done is the energy transferred when a force acts over a distance basically? then i stated that since energy is force over a distance the units are newton metres because Force in newtons into distance in metres gives us these units.

-then i said that since, my definition of energy was that it is what is transferred when a force is applied over a distance, the potential energy of an object, that is the energy it has due to its position, is precisely what energy the force of gravity would transfer to it over such a distance. So to me this kind of worked well with my original definition.

- i then tried to explain that in this model we disregard any conversion of the objects total energy to sound or heat energy, THEN I said that because the only force that is acting on the object is gravity pulling it downwards, it gains speed, but because there is no other force or transfer of energy the energy gained by the force is only the energy transferred to it by the gravitational force. hence Loss in GPE=Gain in KE. Then the easy part where you calculate it using half mv squared. I also stated that while the origin of mgh is easy to deduce, the origin of the formula for kinetic energy comes from one of the SUVAT equations, speicifically, v^2= u^2 + 2as. I dont know how this was derived but it is consisten with all energy calculations and units.

Am I correct im a little confused and I re wrote what i understood here. Id justlike to be corrected if possible sorry ofr the confusion.
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