How do I Circular Platform (force and gravity)

How do I center the gravity and strength? It's like a circular platform (with force and gravity).

Example, the hero runs around the world, but when will jump up, but gravity pulls it back (should be considered the angle)

I put an image to try and help in understanding the above post

[attachment=0:2iu8hvfp][/attachment:2iu8hvfp]

I've done something like this a long time ago on Construct Classic using Physics. You need to apply a constant impulse on the player in the direction of the planet. When jumping you apply an impulse the other way. For walking I'm almost sure friction would work, if the player is a rotating ball

I'll try, but if you have an example to help would be easier

Here are the basics: