Classic example problems of physics buoyancy in grade 9

In the second question, it is necessary to understand the principle of buoyancy. The buoyancy force is only related to the volume of the dispelled liquid and the density of the liquid, i.e., f float = liquid density p the volume v of the dislodged liquid of the object v gravitational acceleration g. The nut falls out, but it should be noted that the whole bottle is suspended in the question stem, indicating that the whole bottle is immersed in water, and the volume v row of the estimated water body is still equal to the volume of 3 bottles, and there is no change.

And the density and gravitational acceleration of water are also constant, so the buoyancy does not change.

In the third question, in order to realize that the submarine can float up and sink, it is necessary to control the relationship between buoyancy and gravity, when the buoyancy is less than gravity, it can sink, and when the buoyancy is greater than gravity, it can float. A bottle of 500ml, the maximum buoyancy of 3 bottles is 3 1000, the buoyancy of 2 bottles is, only one of the working cabins can control the drainage and water injection, that is, only the buoyancy change of the lifting filial piety system can be controlled, if the gravity of the nut is greater, the total gravity is greater than that when the working cabin is filled with water, it can be sunk; When the gravity of the nut is greater, the total gravity of the water injection at the beginning of the working compartment will be greater, which will lead to sinking and cannot float, so the gravity of the nut should be controlled in the nut.

It's not easy to answer, hope, thank you.

During the race, Xiao Wen wants to let the floating submarine sink into the water, and he should go to"Working cabin"Medium fill with water.

In the suspension of the submarine, there are small nuts from"Working cabin"The small hole fell to the bottom of the water, at which time the buoyancy of the submarine"Get bigger"。

If the volume of the metal nut is not counted, in order to realize the floating and sinking of the submarine, the value range of the gravity of the metal nut is: the gravity of the golden nut should be less than the buoyancy to achieve the floating; The gravity of the metal nut should be greater than the buoyancy force to achieve sinking. The specific value range should be determined according to the buoyancy of the submarine, the dust and the mass of the metal nut.

Paraffin wax floats in water and sinks to the bottom in alcohol, so the volume of alcohol discharged in alcohol is the volume of paraffin, and buoyancy in water is equal to gravity equal to the gravity of draining water, so the ratio of the volume of water discharged to the volume of alcohol discharged in the end is 9:10, and the result should be correct, not calculated with a pen.

Let the volume of paraffin wax be v

When a piece of paraffin wax is put into a sufficient amount of water, the density of the paraffin wax is less than that of the water and floats on the surface of the water.

The volume of drained water v water = v (wax water).

A piece of paraffin wax is placed in a sufficient amount of alcohol, and the density of paraffin wax is greater than that of alcohol and sinks in alcohol.

Drain the volume of alcohol v liquor = v

So the ratio of the volume of paraffin drained water to the volume of drained alcohol is:

V water V wine.

v(wax water) v

Wax water.

Agree upstairs, you have to check the density of paraffin, it should be between water and alcohol, in alcohol is sinking bottom, water is floating.

The stone in the diagram refers to paraffin.

1. The gravity of the water discharged by the wooden block is equal to 8 Newtons.

2. The indication is 0.

Auspicious thoughts: 8 oxen's wooden blocks float on the surface of the water, and the gravity of the wooden blocks to discharge the water is equal to the gravity of the wooden blocks. Although the title says that 3 cows of water spilled out of the container, it was confusing.

The plastic bag is filled with water and then placed in the water, where the buoyancy of the water in the plastic bag is equal to the weight of the water in the bag, so the indication of the spring scale is of course 0.

Analysis: 1. The gravity of the water discharged by the wooden block is the gravity of the overflowing water, that is, 3 n in the title, 2. After invading the water, the spring scale has no indication and is 0, because the gravity of the water in the bag is equal to the buoyancy force

1. The magnitude of buoyancy = the gravitational force on the liquid discharged by the object.

So the result is 3n

2. Same as above for zero reasons.

1. Gravity is equal to buoyancy, 8 New, buoyancy is equal to the gravity of discharging water, so it is 8 Nium (note that the overflowing water does not represent the discharged water, unless the container is full), submerged in water buoyancy = gravity, spring scale is not forced.

For example, 1 cubic block of ice has a mass of 900kg. Then the underwater part is the body of the cube (buoyancy = gravity), and the cubic volume left on the water surface accounts for one-tenth of the total volume.

The density of the ice cube is that the buoyancy of floating in water and the suspension of alcohol in both cases is equal to the gravitational force of the ice cube, so the buoyancy of the two is equal.

The density of ice is so ice is floating on top of water and submerging in alcohol. Let the volume v be equal to the force of gravity in water and the buoyancy in alcohol is equal to v* so the buoyancy ratio is 9:8