Hi, why the work done by the gravitational force when a mass moves further away or toward de centre of earth?

Not completely sure what you are asking... but I hope this helps.

Spacetime is a fabric that we can visualize as the surface of a bed. Do you remember the commercial where a man would drop a bowling ball onto a bed that had a glass of red wine on it as well? Imagine spacetime as that surface.

when the bowling ball rests on the surface it creates a large dimple or crater in the fabric that extend out beyond the ball itself. We can say that this "dimple" is the force of gravity exuded by the bowling ball. Think of the Moon as a marble rolling around the ball in the dimple. As the marble revolves within the bowling balls dimple it is Also inside of another Larger dimple(The Sun). When the bowling ball is in between the marble and the "Sun" dimple the marble is pulled closer to the bowling ball... but, when the marble is in the middle it is pulled further away from the bowling ball and towards the "Sun" dimple.

Hope this helps,

Mitchell

I'm not that good at physics, but the way I understand it is that all of the planets in the solar system are in a state of free fall they fall towards the sun after the reach the vertices of the elliptical orbits, pulled by the sun's gravity. Centripetal force won't allow then to straighten their path to fall directly into the sun, so they miss the sun and though they are still being pulled by the sun their momentum moves them away from the sun until the gravity overtakes their momentum and they fall back towards the sun.

Now the idea of work being negative is confusing to me too, but I remember vectors from H.S. physics. They are straigh lines with both magnitude and direction. It's not the work is negative per se, but if you assign a positive value to one vector, then the other vector would be negative? Right? I guess maybe like then you push against something their is a 'normal force' acting with equal magnitude and opposite direction.

Damn now I'm confused lol. Oh, well, I tried. Ask that wheelchair guy.

W = F•d

A dot product can also be represented by:

W = F*d*cosø

So if the body in the opposite direction of the force... itll be between 90<ø<270 so basically itll spit out a negative as cosine is positive in quadrants 1 and 4.

"Every action has an equal and OPPOSITE reaction"

You lift something under gravity and YOU do work. i.e positive work added to the system by you.

Therefore the gravity ( which is equal and opposite ) absorbs that work. i.e GRAVITY does negative work when you lift an object.

When the object falls the opposite is true. Gravity then does the work and you absorb the work.