Correct Answer to Question 4

The vessels have different weights because they contain different volumes of water. Since water depths are equal, the pressure at the bottom due to the water is the same for the three cases. And since the vessels all have the same base area, each of them will experience the same force due to the water.

But there are other forces on the bases: the forces due to the side walls of the vessel.

For example, in the left-hand vessel, the side walls must in part push upward to support some water. So these walls push downward on the base. To keep the base in equilibrium, the scale must push upward - and it's the force due to the scale that we observe. You can apply the corresponding argument to the other two vessels.

Formula Sheet

Question 4

Question 5

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