Question

Part A) The air pressure above the liquid in figure is 0.488 atm . The depth of the air bubble in the liquid is h = 37.9 cm and the liquid’s density is 847 kg/m3 . The acceleration of gravity is 9.8 m/s 2 .

Part B) A ship sailing from the ocean into a fresh water harbor sinks slightly deeper into the water. How does the buoyant force on it change?

1. It doesn’t change at all.

2. It increases slightly.

3. It decreases slightly.

4. It decreases a lot.

5. It increases a lot.

Answer 1

Part B) The answer is 1. It doesn't change at all.

Buoyancy depends on the volume of the ship under water and the density of water. As the ship moves from ocean into fresh water, the density decreases. This is becasue the ocean water has more salts mixed in it. So the ship sinks more to increase the under water volume to keep the buoyancy force constant. This buoyancy force will be equal to the weight of the ship. Otherwise the ship will not be floating. If the buoyancy is more than the weight, the ship will be pushed out of the water until the buoyancy equal the weight and if the bouyancy is less, the ship will sink until it becomes equal to the weight. If in a case when the buoyancy is not sufficient wven when the whole ship is underwater, then the ship will totally sink to the bottom of the ocean.