Physics questions! Ace enter! Ask for expert answers! Physics Questions!!

What may not be clear in this question is why you add a spoonful of milk to the water. Why is milk added? We can see from the title.

In order for students to see the straight line propagation of light. Lighting a cigarette in a transparent glass cover, smoke is actually a very small solid particle, and in the process of light propagation in the smoke, part of it is reflected by the small particles of smoke, so that we can see the propagation trajectory of light. So in the same way, milk is a mixture, the principle is the same, after adding milk to the water, there are also many small particles in the water, at this time the propagation path of light in the water can be clearly seen with human eyes.

It turns out that there are also small particles in the water, but there are too few, and some of them are too small, and when milk is added, the phenomenon is obvious. So what about the answer to this question, guess: light travels in a straight line in a homogeneous medium.

Argument: Ibid.

Guess: To illustrate that light travels in a straight line in the same homogeneous substance, light will be deflected if a cigarette is lit or milk is added.

Argument: Take a glass of water and put a chopstick in it will find that the chopsticks are obviously deflected, which is due to the deflection of light between two different substances.

There are 3 unknowns in this question.

Cylindrical base area s

ob long x p heavy f ox.

This allows you to list 3 equations.

The principle of leverage is two.

Variable handles one.

I guess I can't be wrong.

I won't write down the specific answers.

Hope it helps.

LZ should be confident.

This is not an easy question.

If you can make it, if you are not a senior in high school, then you will naturally be a master.

There's no need to doubt it.

This answer is not science fiction.

You don't have to believe in yourself three. Hehe.

Guess: When light shines inside the glass cover, a bright path appears, which is a straight line.

When the milk solution is irradiated with visualization, a bright pathway appears, which is a straight line.

Argument: Air, and milk solutions are colloidal, and the Tyndall effect will occur.

Guess: Light travels in a straight line in the air, and light travels in a straight line in water (with a straight beam passing through).

Argument: If you see a straight line passing through the glass cover of a cigarette with a beam of light, the guess is correct, and if you can't see it, the guess is incorrect.

If you shine a beam of light on the water that has been added to the milk, if you see a straight line running through the water dripping with milk, you guess correctly, and if you can't see it, you guess incorrectly.

For heat engines, fuel combustion produces total work, and traction is useful work

Solution: (1) The pressure on the ground when the car is stationary f=g=mg= 4n [4 is the power, the same below].

The pressure on the ground when the car is stationary 2 10 5Pa (2) When the car is driving at a constant speed of 90km h, the power of traction p=fv=1000n 25m s= 4w

3) The work done by the traction force of about 250km round trip is w=fs=1000n 8j

The quality of gasoline required for the whole round trip is about 250km

Answer: (1) the pressure on the ground 2 105pa when the car is stationary, (2) when the car is driving at a constant speed of 90km h, the power of traction (3) the work done by the traction force of about 250km round trip in the whole journey; The whole round trip is about 250km, and the quality of gasoline is required.

It should be =w q ah = w mq, then m=w q .

The first time I did this kind of question, it is this kind of question, the work done by the traction of the car is useful work, the heat released by the complete combustion of the fuel is the total work, and the complete combustion of the fuel is not q=mq, I don't know if I understand it, I am also in the third year of junior high school.

Overheating your computer can cause a lot of harm.

Too high a temperature can cause the system to slow down or even freeze.

Too high a temperature will affect the performance and life of the computer, and in serious cases, it will burn the hardware.

Too high a temperature can cause the laptop to malfunction with a blue screen.

Replace the CPU fan with more heat dissipation.

Clean up the dust regularly.

Add a laptop cooling base.

When you pump the bicycle with an inflate, the inflator will heat up, and it is friction that does the work to change the internal energy of the inflator.

Ancient human beings drilled wood to make fire, and it was friction to do work to change the internal energy of wood.

The ice cubes melt into water in the sunlight and it is the heat transfer that makes the internal energy of the ice cubes change.

There are two reasons for internal energy change.

1. Do the work. 2. Heat transfer.

From Physics Elective 3-3

When there is salt in the water, the melting point rises.

And the higher the salt concentration, the higher the melting point.

So salt helps ice water freeze.

Both squeezing and rubbing (i.e., cutting) generate heat.

And the ice absorbs this heat.

It melted. So: the melting of ice cubes is not about absorbing the heat of the outside air.

Also, the melting point of the ice cube is fixed.

Until it melts completely, it's all an ice-water mixture.

Keep it at 0° all the time

First of all, make sure that the increased pressure comes from **, the water does not escape, and the wooden block is paid on the water, which means that the gravity of the wooden block is all pressed on the water, and the introduction is added to the bottom of the container, so just calculate the gravity of the wooden block.

The gravity of the wooden block is equal to the buoyancy, which is equal to the gravity of the water discharged, and the floating volume of the wooden block means that the drainage volume is 300*2 3=200 cubic centimeters, so the gravity of the wooden block = buoyancy = 1000*

The pressure at the bottom of the vessel has increased.

The solution: First of all, the volume of the wooden block immersed in water can be found to be 200 cm, which you will.

Then, the bottom area of the container is 200 cm, so the water level rises by 1 cm, according to the pressure formula: the pressure increases by 100 Pa, and with f=p s, the pressure increases by 2n

Module 2 3 is submerged in water, and the volume is 300*2 3 200 (cubic centimeters), then the water surface rises by 1 centimeter; If the base area is 200, the pressure increases by 200 grams.

Wooden blocks have a volume of 2 to 3 in water, and the volume of drained water is 200 cubic centimeters. This is equivalent to adding 200 cubic centimeters of water to the container without putting wooden blocks, and the height of the water is increased by 1 centimeter. So the increased pressure is 200 grams of water by gravity, i.e. = cow.

The pressure increased by 2 n (g = 10 n kg).

The pressure at the bottom of the container = the pressure at the bottom * the area at the bottom, so only the pressure at the bottom needs to be increased.

After putting in the wooden block, because the volume of the wooden block has 1 3 exposed to the water surface, the volume of 2 3 is in the water, and it can be calculated that the height of the wooden block water ** = 300 * 2 3 200 = 1cm.

Hence increased pressure = density of water * g * water ** height = cm , therefore, increased pressure = increased pressure * bottom area =

1: Pressure to the 3rd power.

Pressure = pressure 1 square meter.

Same as above.

It's been a long time since my brother graduated.

But I know the questions are simple and you need to study them well.