Several buoyancy problems in junior middle school physics. I hope everyone can come in and have a look. Physics. All right, come on in.

1) which is more buoyant, diving in the sea or diving in the river?

Submarine diving in the sea is the same as diving in the river, except that the density P of the sea is greater than that of the river. Because the buoyancy F=pgV, the submarine has great buoyancy when diving in the sea.

Although buoyancy = gravity when suspended, the gravity of submarine replacing seawater in seawater is greater than that of replacing fresh water in river water, so the buoyancy is different.

2) Which is more buoyant when a ship sails in the sea or in the river?

This topic is different from the above. The ship is floating on the water, and the buoyancy must be equal to the gravity, and the gravity of the ship is constant in seawater and fresh water, so the buoyancy is equal. Don't look at the density of water at this time, but because of floating, buoyancy = gravity.

3) Soak common wood blocks in water and concentrated brine respectively. What is the buoyancy of the wood block?

Wood blocks are completely immersed in water and concentrated salt water, which is similar to 1), and wood blocks immersed in concentrated salt water have great buoyancy. The situation is similar to 2) when the wood blocks float in water and concentrated salt water.

As long as we thoroughly understand Archimedes' principle and the balance of forces, such problems are not difficult. Think more and practice more.