a ship dips to a large depth in fresh water as compared to marine water why does it happen
Answers
A ship floats because of a buoyant force that pushes upwards on the hull. That force is equal to the weight of the volume of water that the ship’s hull displaces - think of trying to push an empty bucket straight down into the water. As the “hole” you create in the water (that’s the displacement) get larger, the harder it gets to push it deeper (the resulting buoyant force is increasing)
In another way, you can think of the bouyant force as as the effort the water is exerting to restore its equilibrium with the surrounding surface - that whole “nature abhors a vacuum” thing.
Now, this ship itself ways something, and the weight of the ship down - gravity wants to pull it to the bottom - and the bouyant force is always in equilibrium. The depth that the ship is floating at is the exact point where weight and displacement’s buoyancy balance out - and the ship floats.
A ship doesn’t care what it floats in - only that those two forces are balance. Fresh water is lighter than saltwater by a few percentage points (due to the salt dissolved into it) so the ship will need to sit deeeper, and create a bigger “hole” in the water so as to displace enough water to equal its weight.
Similarly, the temperature of the water makes enough difference to the density (weight) of the water that designations are made between tropical and northern waters when calculating safety margins and such for shipping regulations.