Recent content by pedrom

Symon says: a force is conservative when it's only function of position and its curl is zero, using both facts and the Stokes theorem it can be proven that the closed path integral of the force is always zero, so if the Earth moves along a closed path, the work done by the Sun's gravity is zero...

Could you check if my explanation is plausible? If the Earth wasn't moving in a "closed loop" (on a "perfect world", taking in account just the Sun's gravity) each period of translation would represent some work done by the gravity, but there is no "energy input" on the system to...

Just to make it clear, when I say "fall" I mean make a spiral like movement approaching to the sun. Thanks for your explanation, you gave me a light how to explain to him. Ok, I will try to make some MATLAB simulations to visualize that, thank you.

I can understand the mathematics behind the deduction of "expanded" (using Newton's laws) Kepler's First law that shows the orbits can be only parabolic, hyperbolic, linear or ellipses, but a friend (who doesn't know derivatives and differential equations) asked me why, taking in account only...