Pendulum with not homogeneous attraction

I would like to study a pendulum, not on Earth but only with one fixed mass attract a ball. Considered this fixed mass like a point. No friction on this theoretical study. The ball can move only around a part of circle. There are only 2 forces, F the attraction and N the force from wall (circle). The ball is composed with homogenous material, same density everywhere. The center of mass is fixed and it is in the center of circle of the ball. The center of gravity change always:

- it is more at center when the ball is far away the fixed mass
- it is more at outer circle of the ball when the ball is closed to the fixed mass

When I draw the trajectory of the center of gravity, it's not a circle. This would say the force from wall works.

But N seems to reduce the attraction F due to the non circle trajectory. So, I thought the energy goes to the angular velocity but N anf F don't give a torque because they pass trought the center of mass.

I tested an example with Algodoo software, and it confirm no rotation of the ball, it confirm too the lost of energy, sure it's not a professionnal software, maybe it's an error, like me the software see a non circle trajectory. I put an example, Algodoo is a free software.

images:

f1: the system
f2: 3 positions of balls (examples)
f3: N and F forces, orange point is the center of gravity

So,

1/ The ball have a torque or not ?
2/ The center of gravity described a circle or not ?

Attached Images

	f1.png (15.0 KB)
	f2.png (13.2 KB)
	f3.png (67.1 KB)

Attached Files

test circle inside 3.zip (18.6 KB)