Question

Why does a ship rise up in the water when it passes from a river to the sea?

A. The ship is less sheltered from strong winds while at sea and these winds push up the ship.
B. The ship lightens its load before going out to the sea.
C. The seawater is more dense than the water in the river.
D. The waves of the sea push the ship up in the water.

Answer 1

Hint: First try to figure out all the reasons behind this phenomenon of rising up and sinking down as requirement. Then look into the question to check which of the points that are given as options matches the reasons we figured out. Actually rising up and falling down in the sea means that the ship is actually balancing its weight with the weight of the water.

Complete answer:
We all know that the river water is less dense than the seawater, So as the seawater is denser it also exerts more buoyant force than the river water. So as a result of this buoyant force the volume of the ship immersed inside the water increases and decreases according to the density to balance the weight of the ship, so that’s why the ship rises in the river water.

Now, Considering option A it says:
The ship is less sheltered from strong winds while at sea and these winds push up the ship.
This option is totally irrelevant to the question as there is no question of winds pushing up a ship.

Considering option B it says that :
The ship lightens its load before going out to the sea.
If there is a case that the ship will have to move from a sea to a river and there is no port to lighten the load of the ship then in that case will the shipmen throw out all the goods? This option is also not feasible.

Considering option C:
The seawater is more dense than the water in the river.
This option is the correct explanation of the question given due to density the ship tries to balance its weight by sinking or by floating more.
So this option is the correct option.

Option D:
The waves of the sea push the ship up in the water.
The waves of the sea cannot push the entire body up at a once so it is not the correct option.

So, the correct answer is “Option C”.

Note:
We must remember what is buoyant force and what is the role of buoyant force in this question. We must remember how the ship behaves in a denser water and is a less dense water.