re: #133 ludwigvanquixote

Take your first insight about how hard it is to push on the Earth because it has much greater inertia (from its much greater mass). Now…

Imagine you have a block with a spring on it’s bottom like this…

]~~~[]

And you compress it like this…

]~[]

And no imagine that the spring is NOT attached to the Earth.

What happens…

The block is your torso and the spring is your legs.

How do you jump up?

Well, once again, I’m a little confused by the question (this being perhaps a good example of each student requiring an individualized way of grasping things, and not all of them responding to the teacher’s visualization example).

How do I jump up? Well, in your scenario I jump up if the torsion of the springs has a greater potential energy than the energy it would require to pry the two bodies apart in the distortion of that particular gravity field.

If the springs are tiny and feeble, I don’t go anywhere because their potential energy is miniscule compare to the force holding me where I am. If the springs are giganticaaly powerful, they might sproing me up so far that I would exit the gravity well of the other mass-body and achieve escape velocity. If the springs are “just right,” then we see a special case of me moving a short distance in the gravity field, gaining potential energy as I move away from the center of the other body’s mass — and then since I haven’t reached orbital or escape velocity, I run out of juice and expend my energy falling back down to the same bottom of the gravity well I was in before.

Hmmm…I get the feeling this is not the answer you were looking for. I made it a hundred times more unnecessarily complicated. Sorry!