Seeking junior high school science is prone to mistakes or misunderstandings

Summary. Hello dear! We'll be happy to answer for you.

According to Archimedes' principle, the buoyancy experienced by the submarine is equal to the weight of the drained water, and the weight of the drained water is equal to the density of the water multiplied by the volume of the drained water. Therefore, we can calculate the volume of water discharged by the submarine by the following formula: v = f g where v is the volume of water discharged, f is the buoyant force, is the density of the water, and g is the acceleration due to gravity.

The substitution number is worth: v = 10 7 n 1000 kg m 3 m s 2) v = m 3 Therefore, the volume of water discharged by the submarine is cubic meters.

A detailed parsing process of this.

Hello dear! We'll be happy to answer for you. According to Archimedes' principle, the buoyancy to which a submarine is subjected is equal to the weight of the drained water, which is equal to the density of the water multiplied by the volume of the drained water.

Therefore, we can calculate the volume of water discharged by the submarine by the following formula: v = f g, where v is the volume of water discharged, f is buoyant, is the density of water, and g is the acceleration due to gravity. The number of substitutions is worth it:

v = 10 7 n 1000 kg m 3 m s 2) v = m 3 Therefore, the volume of water discharged by the submarine is cubic meters.

Not according to Archimedes' law, I'm asking how is this equation calculated?

Hello dear! The buoyancy experienced by the submarine while suspended is 107N, and this buoyancy is generated by the buoyancy force of the water on the submarine. When a submarine is suspended in water, its gravity is equal to the buoyancy of the water on it, so it is able to remain suspended above the surface of the water.

The magnitude of this buoyancy depends on the volume of the submarine and the density of the water, as the buoyancy is equal to the density of the liquid on the water multiplied by the volume of the object multiplied by the acceleration due to gravity. In this case, the buoyancy of the submarine is x 107 N plus 105 N, which is due to the extra 1 g of gravity that it is subjected to. Because of this, the total buoyancy is 107N.

1Place the corner of the towel in a basin of water, and the whole towel will slowly become wet, explaining this phenomenon capillary phenomenon).

2In hot weather, sprinkle some water on the ground, the room will be cooler, why?

Evaporative endothermy).

3In wet weather, wet clothes are not easy to dry, why?

The ambient vapor pressure is high).

4Fog often grows early in the morning and recedes before noon, why?

Fog is the result of water vapor condensation, and when the temperature is high, the water vapor will naturally evaporate 5 Why is there always an iron chain at the rear of the tanker truck dragging on the ground?

To prevent static electricity, the static electricity generated by the friction between the oil and the car can be directed to the earth)6 Sometimes there are a few white clouds floating in the blue sky, why are these clouds white?

White is actually a mixed color, because clouds can absorb a variety of colors )7 What are the benefits of using a red light to indicate a stopped traffic signal? Why not use blue or purple lights?

Red light has strong penetration, and blue and violet light generally travel at a short distance).

Question 1 c Not necessarily, because the pulmonary veins, which pass through the pulmonary circulation and return to the heart, are rich in oxygen. That's why it's called "arterial blood."

Question 2 A Question 3 C Because it is excreted in the urine, when it enters the kidneys through the systemic circulation, it does not flow back into the heart.

The first topic is b, the metabolic characteristics of children and adolescents should be that alienation is greater than assimilation, at this time, people want to grow and develop, and metabolism is fast.

The second question is the method of making a blood smear: take another slide with a smooth and flat edge as a push piece, and the push piece is about 20 30 ° with the slide, and contact with the blood droplet, so that the blood droplet is scattered on the edge of the slide, and quickly push the slide to the other side of the contact blood droplet.

The third question is C, which is the drainage of this part of the water before it flows into the renal veins.

Below the spring scale, there is a weight of 5 N hung, when the weight is stationary, the reading of the spring scale is (equal to) 5 New, when the spring scale pulls the weight to drop at a constant speed of meters and seconds, the reading of the spring scale is equal to 5 N When the spring scale pulls the weight up at a constant speed of 1 meter second, the spring scale reads equal to 5 N. （

The reason why you have such an idea is also normal, the magnitude of the inertia we usually talk about is indeed determined by its mass, but we say that inertia is the property of an object to maintain its original state of motion. So when is it used? That is, when the motion state of the object changes, it is related to inertia, for example, it is a force acting on 1n, and I want to accelerate the object to 1m s, and the mass is large, and it takes a long time.

Or, if it is a force of 1n that stops two objects, then it will take a long time to have a large mass. However, in this problem, the object is not stopped, but still moving at its original velocity. There is no change in the state of motion (change in speed) and therefore, it is not related to mass.

Another example, for example, if two objects are moving at the same speed now, and you push them with the same amount of force to stop them, then the object with the mass takes a long time.

A Because the surface is smooth, after the car is stopped, the two objects still maintain the original motion speed due to inertia. The two are relatively stationary, so they do not collide!!

It should be A

When two objects move in a uniform straight line with the car on the smooth horizontal plane of the car, the two objects remain relatively stationary.

When the car suddenly stops moving, the two objects continue to maintain a uniform linear motion because of inertia, the above Frankfurt said, the mass of the object is related to the inertia of the object, this sentence is true, but the inertia of the object has nothing to do with the speed of the object, therefore, the two objects still remain relatively stationary, and the two objects must not collide.

Thank you!!

(1) As I said in (3), the magnitude of mass only affects the magnitude of friction, but the acceleration needs to be divided by friction by mass, that is, the acceleration of both cars is a=g, and the speed of the object stopping is only related to the acceleration, not the mass.

2) No friction, this situation is relatively simple to analyze, because there is no friction, after the car stops, there is no resistance to the two objects, so the two will move at the same speed and never touch, so choose A;

3) There is friction, when the car stops, the car has frictional resistance to the two objects, and f=mg*, that is, it is related to the mass, but the acceleration has nothing to do with the mass, it is always a=g, and the initial velocity is the same, so the two will do exactly the same deceleration motion, so the two will never collide, so it is still a choice;

To sum up, in either case, it is right to choose A, but the analysis process is different!

Although there is no picture, I can think of it.

The car does a uniform motion and suddenly stops, will give the above two objects an equal forward inertia force, these two forces are the same So this question mainly lies in the size of the resistance between the two objects and the surface of the car, the title mentions that it is a smooth surface and long enough, indicating that the resistance is negligible, since the two objects are subjected to the same forward inertia force, the backward resistance is the same, the distance between the positions of the two objects is the same, so they must not touch, so choose A

To answer your supplementary question): The magnitude of the inertial force has nothing to do with their mass, this force is an inertial traction force given to them by the car when the car suddenly stops, this force is fixed, their mass is only related to the resistance, but the surface smooth resistance is negligible, so the 2 forces are the same so it is a.

A because it's long enough and the surface is smooth, they're going to move in a straight line at a constant speed.

I didn't know about this question at first, but then I figured it out, I promise that I won't touch it, if you don't understand, you can ask me.

The surface is smooth and there is no friction, when the flat car stops, the two objects have no other external force except for the action of gravity, so the two objects will continue to move forward at the original speed, which can be seen from the uniform linear motion of the two objects with the flat plate before.

Both have the same velocity, so the two objects must not collide.

There is no picture

Yes, a horizontal frictionless surface depends on inertia.

Inertia is only about mass, so if the latter one is heavier than the previous one, it hits, understand?

So choose D

Don't listen to Frankfurt on the 3rd floor, you can go to the bus and see if the fat man is going further when he brakes...

The object will maintain its original velocity.

The mass is large, but the speed is difficult to change!!

a According to the inertia "the object has the original uniform linear motion state or stationary state", the original object is doing uniform linear motion, therefore, when the trolley stops, the two objects are still moving in a uniform linear motion, and the distance between them is still the original distance.

m1 m2 with the car together on the horizontal table to do a uniform linear motion, when the car suddenly stops moving, their speed is the same, no external force, so always move at the original speed.

Note: The speed is the same.

(1) The mass of solution a: m = v = gram cubic centimeter centimeter centimeter 3 = gram. Then the mass fraction of solution A is:

Gram = 25%; (2) The mass fraction of solution b is (because the density is approximately gram cubic centimeter, so the volume conversion to mass in the following calculation is omitted in one step) :(g 25%) g =; c solution mass fraction is: (g g = ; d The mass fraction of the solution is:

Gram=; Because solution B is equivalent to dilution 10 times, solution C is also diluted 10 times, and solution D is diluted 5 times, so it can also be listed as: g g 10 10 5=; (3) Because the mass fraction of the final solution is, the mass of the liquid that can be prepared is: grams, that is, v = m = 2000 grams of grams of cubic centimeters = 2000ml

1: The mass fraction of the mass in solution A (25%) 2: The mass fraction of the solute in the final experimental needle solution D ( Can gram streptomycin be prepared into (2000) ml of experimental needle solution? 4*10*10*5

The preparation method of the liquid medicine of the streptomycin experimental needle for injection is as follows: 1. Dissolve grams of streptomycin in water to make milliliter solution A; 2. Take a milliliter of solution A, dilute to milliliter with water to obtain solution B; 3. Take a milliliter of solution B, dilute it to a milliliter with water, and obtain solution C; 4. Take a milliliter of solution C, dilute to a milliliter with water, and obtain solution DDue throughout the formulation.

2 A chemical reaction is when a new substance is formed, so it should be a chemical reaction or rather a nuclear reaction.

4 For example, plastics are a lot of small molecules, connected together, the exact number is not fixed, about 1,000 or more.

8 In industry, it is generally done directly from the air in the laboratory, calcium carbonate plus hydrochloric acid9 Common metals are reducing agents, and there are some gases such as CO H210 condensation.

Everything else is the same as upstairs.

The last question is to vaporize first and then liquefy.

Water vapor is invisible.

White gas is tiny liquid droplets formed by the liquefaction of water vapor.