Do you not just do the triangle formula? When you multiply A and B for example, and end up with C... then when you divide C by B, you are left with A. And the same thing works for C over A. Not sure...
Let's not get into a shouting match over the definition of acceleration. This thread is for the OPs benefit.
There are a lot of ways to define potential energy. You can have gravitational, electromagnetic, spring, chemical, etc. I would assume that, for an introductory physics course, we are dealing with gravity. I asked the OP for his class / teacher / book 's definition of potential energy. Once we have that we can give him a better answer.
hmm.. i think it is wrong, because d=/=h. Work counts as force * horizontal change of object position. So please remeber that. When you want transport package (f.e 5th floor) using elvator.
Your work will equal as 0.
Because.
W= 10N * 0m = 0J
But when you use the same force while moving 1m. You will get
W= 10N * 1m= 10J
Also I dont know why you used that equation. Problem is simple.
potential energy Ep=mgh
while g=(GM)/(R^2)
M-Earth mass
G- is gravity constant = 6.67
There is no Work when object is falling or elevating. Only sideway move change that. <<< Remember that for life
That is not correct. To lift something (apply a force for some distance), you must do work against gravity. The whole point of OP's question is to show that a change in potential (i.e. lifting / lowering) is equivalent to work.
Hopefully that's what we're working with. A more general relation might require some calculus :x
Last edited by Monolith of Mazes; 2013-01-28 at 05:02 PM.
Sorry but the definition of work done is the product of the force and the displacement in the direction of the force. Since gravity acts downwards, work is done by gravity when an object falls and work is done against gravity when an object elevates. There is no work done by or against gravity when an object moves sideways (horizontally) in a gravitational field.
Last edited by Zedra; 2013-01-28 at 05:07 PM.
Isn't this covered by conservation of energy and the first law of thermodynamics?
It is by caffeine alone I set my mind in motion. It is by the beans of Java that thoughts acquire speed, the hands acquire shakes, the shakes become a warning.
-Kujako-
If the problem is to prove that potential energy is a form of work(stored work). Then the solution to the problem uses units.
Basically take the equations and put in the units of the variables.
W=Fxd=m(axd)=kg(m/s^2)m=kgm^2/s^2 which is also equal to a joule(j)
GPE=gph=mgh where g=9.8m/s^2 so mgh=kg(m/s^2)m=kgm^2/s^2=j
You can use any potential energy formula and get the same units as work which means that potential energy can be converted to work.
Yeah units would work (pun intended? maybe ;D ). You're still using U = mgh F = mg W = Fh, though. You do say that you can use any potential formula and get joules, so yeah unitary analysis would be a better general solution. Depends on what his teacher is defining U as. Hopefully OP is still lurking around and can get some benefit from our tireless pondering.
Sorry english is not my native languge so you may not understand me properly.
W=F*s*cos(a)
so as you know from math
cos(90)=0
that means that work looks like this
W=F*s*0
so
W=0
OT: But all i can come up with is
( i dont know how to clearly write integral down so i attach img)
So Force depends on the position of points A and B
Last edited by mmocc05c784250; 2013-01-28 at 05:55 PM.
Thanks a lot for all of the help I got in this thread, it was all helpful, even though it was initially a little hard to understand most of it. Thanks!
Last edited by mmoc58a2a4b64e; 2013-01-29 at 03:39 AM.
PUH-lease. I just got home and scrolled through the thread and everyone just repeated what I said in a different presentation. Like I said. It was all me. I know it and you know it.
But yeah this question isn't really hard the way you're making it sound, you should be fine.
Last edited by mmoc58a2a4b64e; 2013-01-29 at 03:39 AM.
The Work-Energy Theorem states that Work is equal to a change in kinetic energy.
W = delta KE
The Law of Conservation of Energy states that the total energy of a system remains constant.
E = PE + KE = const.
Therefore, a change in potential energy will cause a change in kinetic energy (to maintain conservation). But a change in kinetic energy is equal to work, according to the W-E Theorem. Thus, a change in potential energy is equivalent to work.
That's my version of the solution without the need to invoke any specific types of potential energy or other equations.