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- Homework Statement
- Suppose we put a glass upside down in water at a high speed. Therefore, the air inside does not escape. As the glass goes down in the water, the pressure increases and the air inside the glass is compressed (its volume decreases). How to apply the force F so that the object moves downwards at a constant speed? (The depth of the container is infinite.)

- Relevant Equations
- Newton's second law

Archimedes' principle

My answer : According to the question, the glass and the air inside it entered the water. Let's assume that the net force becomes zero at a moment, that is, the sum of the weight force and F is equal to the buoyancy force. By going down in the water, the gas volume decreases, so the buoyancy force also decreases, as a result, F also decreases. From time to time, the gas volume stops decreasing, as a result, the buoyancy force and F remain constant. So F decreases after equilibrium and remains constant after stopping the decrease in volume.

Can someone tell me Why my answer is wrong ?!

Can someone tell me Why my answer is wrong ?!