A lever scale is balanced with a beaker filled of air on one side. The scale is very sensitive and can easily measure a change in weight of about 1/2 mg.
What happens If you put your finger carefully into the beaker without touching the glass?
since you displace some of the air in the beaker, its side of the lever should rise.
I don't think it is correct but i am myself not sure what is the right answer.
Yeah, you may be right. It could be that the hydraulics involve prove that the weight of air in the beaker remains constant regardless of how much is displaced, but I'd have to research it. I guess you can do that on your own, or hope Damon or someone will stop by with greater expertise.
If you put your finger carefully into the beaker without touching the glass, it means that your finger will displace some of the air inside the beaker. The air that is displaced by your finger will create a change in weight on that side of the lever scale.
Since the lever scale is very sensitive and can measure a change in weight of about 1/2 mg, it will detect this change. The weight on that side of the scale will increase slightly due to the displaced air, causing the lever to become unbalanced.
As a result, the other side of the scale will rise slightly since there is no change in weight on that side. The amount of rise will depend on the volume of air displaced by your finger.
In summary, if you carefully put your finger into the beaker without touching the glass, the lever scale will become unbalanced, with the side containing the beaker rising slightly.