@Pappenheimer
Yes, i have the jitter problem sometimes. It is not visible in the video but if you get very close you can hear it jittering, but not too often.

In the demo there are objects weighing 10 units(barrel,ball etc.) and 100 units(trucks). Heavy objects moves slower, light objects moves faster. I used heavy objects to show this but i think it is not very clear in the video. I can put a demo after some tidyin up. It will be more clear while playing.

For very light objects, the power of the gun must be decreased. This is normal. The cardbox looks hevay because of this. It's my fault. Instead of decreasing the power of the gun just for the cover(it weighs 1 units), i decrased it for the whole box.
Thank you all for your comments.