Ask a simple question about physical buoyancy in the second year of junior high school Urgent! Urgen

The conversion between volume and weight units must introduce the density p. ** and the density of refined oil PT indicates that at a certain temperature, the volume of oil per cubic meter is P tons. The conversion relationship is:

The volume of a ton of oil = 1 p. cubic meter.

The equivalent number of barrels per ton of oil = 1 p * barrels (oil).

Divide by density to find the conversion factor formula for how many barrels of oil 1 ton of oil is equal to. The size of this conversion coefficient is related to the density of the oil, and it is the reciprocal relationship with each other, such as: Daqing ** density is, Shengli 101 oil depot ** density is, can be obtained separately:

Daqing**Conversion Factor=, Victory**Conversion Factor=

The world's average specific gravity** is usually measured in terms of 1 metric ton = barrel (42 US gallons per barrel) or 1,174 liters.

The same is true for petroleum products. For example, the density of a certain gasoline is, and the calculation result is: 1 ton of gasoline is equal to a barrel; The density of a certain diesel fuel is calculated as 1 ton of diesel fuel is equal to a barrel. And so on.

Barrels and tons are two common units of quantity. Western countries such as OPEC and the United Kingdom and the United States usually use barrels to express their units, while countries such as China and Russia often use tons as their units. The conversion relationship between tons and barrels is:

1 barrel liter = 42 gallons. US L gallon = liter, Imperial 1 gallon liter. If you want to convert volume to weight, it is related to the density of **.

Suppose the density of a property is kilograms, then the weight of a barrel is kilograms.

1. If you calculate the volume, there will be decimals, which is incorrect.

It should be a floating object, f float = g

Solution: g wood = density * volume * g = ......=

The buoyancy is 120N

2. The density of ** * the volume of the water discharged * g = the density of the wood block * the volume of the wood block * the density of g ** * 2 3 The volume of the wood block = the density of the wood block * the volume of the wood block.

Bring in the density of the wooden blocks. **The density is two-thirds of the density of wooden blocks.

**Density is:

3. Knowing the density of **, you can calculate the volume of one ton**.

Do one more division and the answer will come out.

Approximately equal to barrels. In physics, you should be flexible in choosing formulas, and whenever you see a floating object, you must remember that f float = g

If you are familiar with the principle of buoyancy, the cause method, the weighing method and the Archimedes formula, you can choose the method more flexibly to solve the problem.

This question is given less g=.

By f float = oil g v row (2 3v wood) = g wood = wood g v wood, so 2 3 oil = wood, oil =.

f buoyancy = x2 3 200 10 -6m 3=.

1 ton can hold 1000kg (barrel) = 6 and 2 3 barrels.

It can be announced by Archimedes, but the object must be of uniform density, and if the density is not uniform (such as a hollow object), it must be calculated by the balance of two forces, that is, buoyancy is equal to gravity.

According to Archimedes' formula, the magnitude of the buoyancy is equal to the gravitational force of the liquid from which it is displaced, so it should be the density of the liquid, the volume immersed in the liquid (not the total volume of the object).

If it is a little exposed, if it is floating, it is generally calculated by the floating condition f float = g.

It is also sometimes calculated by using the upward pressure * bottom area of the bottom surface.

OK. But v should be submerged in a volume below the surface of the water.

Yes, it is not enough to calculate the area of the object in the water, the density, the weight is constant, the more the area of the object and the water contact, the greater the buoyancy will be subjected, to put it simply, you put a wooden block, from the floating water slowly press into the water, the force is getting bigger and bigger.

v in the formula is the volume of water discharged by the object, if the object is completely submerged in water or suspended, this volume is equal to the volume of the object;

If the object is floating, the question will generally tell you the volume of water to be discharged or the gravity of the water to be discharged;

When an object is suspended and floating, the buoyancy can also be found according to the balance of two forces, which is equal to the gravitational force of the object.

Now the high school entrance examination generally does not directly test the formula of f float = p liquid v row g, and now the formula of float = g row = m row g is used.

Float = g row = m row g = p liquid v row g

When floating, levitating:

f float = g matter.

Volume generally refers to the displacement, the volume when floating is equal to the volume of the object immersed in water, and the volume is equal to the volume of the object when suspended.

v refers to the volume of water discharged by the object.

In the case of levitation, v is equal to the volume of the object; If it floats, the object is not completely submerged in the water, and v is equal to the volume submerged in the water, that is, the volume of the water discharged.

Float = g row = m row g = p liquid v row g

When floating, levitating:

f float = g matter.

v is the volume of water discharged by the object, the buoyancy of the object is equal to the gravitational force of the water it displaces, and the buoyancy and levitation are the buoyancy equal to the gravitational force of the object.

The volume of water discharged twice by A is the same (because they are both completely submerged), so the benefits are the same (A pair) The first time A is buoyant, A gravity and rope tension, the second time A is buoyancy, A gravity and C gravity, the first two forces are not the same, the third force should also be the same, so the rope pull force and C gravity are the same (B pair).

B is suspended in water (and there is a rope pull), and the density cannot be smaller than that of water (C is wrong) B is subject to buoyancy, gravity and rope pull are balanced, B gravity buoyancy rope pull, and we know from b the rope pull C gravity, so B gravity buoyancy C gravity, that is to say, B is heavier than C (D pair) and chooses C

For A, both are submerged in water, so the buoyancy force on the A block is equal to A.

The difference between the gravitational force and the buoyancy force of A is the same in both cases, so the pulling force of the rope is equal to the gravitational force of the C object b is correct.

If B's density is less than water, then, B floats, so c is incorrect B's gravity minus B's buoyancy is equal to C's gravity, so B's mass is greater than C's mass, d is correct.

To sum up, choose C

A is correct, because A is submerged in water, and the buoyancy depends on its volume, so the buoyancy is equal;

b is correct, A is in equilibrium by the three forces, gravity and buoyancy are the same, then the tension and pressure are the same;

c False, the density is greater than water, otherwise it floats;

D is correct, C's gravity is pressed on A, and B must overcome the buoyancy first, and the remaining force will pull A.

c, B has been fully immersed in water, and B's density will not be less than that of water. A, B are easy to understand. d：

The volume of water discharged in Figure 1 is greater than Figure 2, that is, there is, F float 1 figure is greater than F float 2 figure and both figures have: F float = g total (floating, suspended), and the gravity of A is certain, so it can be pushed, g B > g C.

C is wrong. It is evident that B Lajia was submerged in water. It's like a stone pulling a block of wood and submerging it in water.

A is buoyant = water density * g * v row, so A is subject to the same buoyancy, so A is correct, B is correct, and the question is incomplete.

The buoyant force experienced by an object is the gravitational force exerted by the water it expells. As long as you understand this, the question of buoyancy is at hand.

These things should be done by yourself, and only by doing it yourself once can you have a deep understanding. Later in life and work, these basic knowledge can bring you unexpected inspiration.

The buoyancy of an object is equal to the gravitational force it exposes to the liquid, then the volume of the first wooden block is 1000 cubic centimeters, one-fifth of the water surface is exposed, the drainage volume is 1000*4 5=800 cubic centimeters, and the density of water is 1g cubic centimeters, then the buoyancy of the wooden block is grams and kilograms)* The direction of buoyancy is opposite to gravity: vertically upward.

Similarly, the second question The buoyancy of the glass ball in the air is negligible, and the gravity of the ball is considered to be the buoyancy of the water Then the volume of the glass ball is the volume of water, and the volume density of the ball is easily solved, and the following problem is the same!!

The volume of the wooden block is balanced twice, and the ratio of the volume of the water part to the total volume is constant, so that the volume of the wooden block is vcm3, then 32 v=24 (v-32), and the solution is v=128cm3

The gravity of the wooden block = buoyancy = the gravity of the water it dispels.

The volume of drained water = v-32 = 96 cm3, and the mass of this part of the water is 96g wood block density = 96 128 =

The block floats twice, and the buoyancy in these two processes is equal to the gravitational force of the block.

The first time: the gravity of the wood block is: the density of the wood block * g * v wood.

The buoyancy is: the density of water *g * (v wood - 32 cm3) This is according to Archimedes' law.

The gravity of the wooden block is equal to the buoyant force, that is, the above two are equal, getting.

Density of wood block * g * v wood = density of water * g * (v wood - 32 cm3) (first formula).

The second time: the gravity of the wooden block is: the density of the wooden block * g * (v wood - 32cm3).

The buoyancy is: the density of water *g * (v wood - 32 cm3 - 24 cm3) It is also based on Archimedes' law.

The gravity of the wooden block is equal to the buoyant force, and the density of the wooden block * g * (v wood - 32cm3) = the density of water * g * (v wood - 32cm3 - 24cm3) (second formula).

There are two unknowns in one or two formulas, which are the volume of the wooden block and the density of the wooden block required by the problem.

It's a binary system of equations, it's easy to solve, you can just solve it yourself.

Solution: 24 cm3 from the bottom means that the weight of 32 cm3 is equal to the weight of 24 cm3 of water.

The mass of 24 cm3 water is: 24 g.

Then the density of wood is: 24 32=, that is, 750kg m 3 wood block volume: 32 ( cm3

Remember, you should use the two volumes and the density of water together.

There are some problems with the topic.

1. If p A p B p water.

Then the ratio of buoyancy is equal to the ratio of their volumes, which is equal to 1:2, and the answer is a

Of course, if the water is deep enough, then the balls will never stand still, because they will always sink (ignoring the change in water density caused by water pressure), perhaps this can rule this out.

2. If p water, p a, p b.

Because it is deep enough, both balls are in a floating state, buoyancy is equal to gravity, and the mass is equal, so the buoyancy is also equal.

The answer is b

Choosing a deep enough water is understood as completely immersed in water, so that the mass is the same, the density is 2:1, then the volume is 1:2, and the buoyancy is only related to the volume of the water discharged.

No way, your supplement is to let the object float naturally on the surface of the water or sink to the bottom, deep enough can you understand? That is, the density is less than that of water, and those that can float on the surface of the water will be pressed down, so it has nothing to do with their relative density of water. You can ask your physics teacher if I'm right.

At that time, I also got a perfect score in physics in the college entrance examination.

It is discussed in several cases.

1. p A p B p water: according to Archimedes' principle, it can be known that f A: f B = 1:

22. P A P B = P Water: According to Archimedes' principle, F A: F B = 1:

23, p A p water p B: A sinks, the buoyancy f A = p water gm p A, B floats buoyancy f B = mg

So f A: f B = p water: p A.

4. P A = P water P B: A is suspended, the buoyancy f A = mg, and the buoyancy f B = mg is floating

So f A:f B = 1:1

5. p water, p A, p B: A and B are both floating, and the buoyancy is equal to gravity, so f A: f B = 1:1

Therefore, A, B, and D are chosen

B is twice as much as A, so B is twice as buoyant as A, so B is twice as buoyant as A, and this is because the density of the ball is greater than that of water, and if both balls are less dense than water, then the buoyancy is equal.

b water is deep enough for buoyancy to be equal to gravity at rest.

Is it still needed? I have a lot of this, if you need it, I will send it to you in the form of a document, because this ** can't be displayed

Analysis of typical examples of physical buoyancy in junior high school.

Example 1 Which of the following statements is true (

a The deeper an object is submerged in water, the greater the buoyancy it is subjected to.

b Denser objects experience greater buoyancy in water.

c Heavier objects are less buoyant.

d The same volume of iron and wood is as buoyant when submerged in water.

The mathematical expression of Archimedes' principle is: , the formula shows that the amount of buoyancy experienced by the object is only related to the density of the liquid and the volume of the liquid discharged by the object According to the formula analysis of the content of the title, the problem can be solved

Solution A option: The object is submerged in water, regardless of the depth, the V row does not change, the density of the water does not change, the F float does not change A option is incorrect

Option B: The buoyancy experienced by the object is not directly related to the magnitude of the density of the object, option B is incorrect

Option c: The magnitude of gravity has no effect on the buoyancy of the object For example, a large piece of iron is heavier than a small piece of iron, but if you submerge the two in water, the large piece of iron will be more buoyant because the large block of iron has a large V row The c option is incorrect

Option D: Iron and wood blocks of the same volume, submerged in water, the same V row, same, f floating iron f driftwood, the iron and wood are subject to the same buoyant force

Answer d Note: The buoyancy of an object has nothing to do with the object's own gravity, its own density, and its own shape

Example 2 What is the density of an iron block with a mass of 79g? How much does it weigh? Submerging this piece of iron in water, what is the mass of the drained water? What is the buoyancy experienced? (g takes 10 n kg).

This question tests the difference between the formula for calculating the gravitational force of an object and the formula for calculating buoyancy