Case I: A trajectory placed in the path of a planet's orbit

Here, a trajectory is placed stationary in the path of a planet's orbit. Now this trajectory has no mechanical energy to speak of. Now as the planet approaches the object the object comes under the influence of the planets gravitational field and moves towards it. Now what happens is, the object fall onto the planet and then I, standing on the planet's crust put a turbine down at exactly the point where the object's gonna fall, such that the object hits the turbine's blades and converts its K.E. to electrical energy which I store in a battery. Now my question is, where did this energy come from for the trajectory had none to speak of. Now you might say that the planet's in motion so it's the K.E. of the planet so consider Case II.

Case II Objects A and B

Two objects A and B are placed together in a vacuum such that their Gravitational Fields touch each other at a single point. In the beginning they had no mechanical energy to speak of, but as they enter each other's gravitational field they move and gain mechanical energy. Now after doing this I ask you the reader, have I created Energy out of nothing?

P.S. I am still in high school(1st year), so if this questions do seem childish do excuse me for my actions. Also try to explain your answers in a way I could easily understand them.

P.P.S. Is there an easier way to make diagrams besides Paint? I have been wasting a lot of time making diagrams.

  • $\begingroup$ « Here, a trajectory is placed stationary in the path of a planet's orbit. Now this trajectory has no mechanical energy to speak of» I don't think you meant trajectory in that phrase of yours, as it makes no sense. $\endgroup$ – user154997 Oct 22 '17 at 10:43
  • $\begingroup$ Yeah I am Indian, still struggling with my English :P $\endgroup$ – Captaine Code Oct 22 '17 at 10:48
  • $\begingroup$ There is no limit to the range of the gravitational fields, so your diagram of Case II doesn't make sense. In a Newtonian sense, any two masses in the same universe are interacting gravitationally. With that information, one must then decide which gravitational interactions are important and which can safely be ignored. Considering the mass of Earth, for a falling object we can safely ignore the gravitational interactions between the object and other objects at the surface of Earth. $\endgroup$ – Bill N Oct 23 '17 at 16:55

For "trajectory" use "mass in a trajectory"

I) It came from gravitational potential energy of the smaller mass. That mass is higher up, and falls to earth, releasing this energy as kinetic (mechanical) energy.

II) You have not created energy from nothing. Total energy is always conserved over time. The kinetic (mechanincal) energy comes again from the gravitational potential energy. Imagine that energy was at one time put in to the system to separate the objects against their gravitatational attraction.

Paint is about as simple as it gets when it comes to diagrams. Unless you are able to draw them on paper and scan them in, that is easier.

  • $\begingroup$ Sorry I forgot mention that the not of any planet or anything but was freely floating in space. So I didn't make it go higher, henceforth it had no mechanical energy to speak of. Sorry for the inconvenience. $\endgroup$ – Captaine Code Oct 22 '17 at 10:57
  • $\begingroup$ The point is, you may not have put the energy in (aka "made it go higher"), but that was done at some point after the beginiing of the universe. $\endgroup$ – JMLCarter Oct 23 '17 at 1:04

Not the answer you're looking for? Browse other questions tagged or ask your own question.