There are a few physical problems that bother me

Physics is originally based on factual phenomena, but it is necessary to think about the objective existence of facts in order to summarize theories, and there are too few experiments that can be done at this stage, junior high school is more or less about some daily phenomena, the more you think about the better, many theories in junior high school are very simple, with the existing just can't explain or can't explain, but can cultivate the habit of thinking, which is very helpful for future learning.

But in the future, if you don't want to do too much research on physics, then don't think too much, just remember the formula, it's very simple, it's easy to score.

If you can't think of it, don't think about it first, relax first, then re-read the question, rethink it, don't think about the places you can't think of, unless the road is ......

You're new here, and I have a learning method here: just understand in class, and don't really take too many notes; Don't be stopped by teachers, classmates, etc.; If you don't understand, you must understand; No matter how difficult it is, as long as there is hope for a solution, don't give up!!

I have just entered the second year of junior high school, and after studying physics, I found that there are many problems that are not in line with the textbook, for example, in the fourth chapter of the textbook, it is said that water is thermal expansion and cold contraction, but after the water freezes, the density becomes smaller and the volume becomes larger, how can this be explained? Later, I asked the teacher, and the teacher said that the current science could not explain this phenomenon. If you don't understand or have your own thoughts, just go and talk to the teacher, the teacher can give you a satisfactory answer to a large extent!

I'm not a teacher).

A lot of people do.

Go to junior high school or high school.

It's not as good as before.

You can change the way you read books.

How I read it.

There is no dead reading.

It's useless to read books to the death.

Have your own way.

You can ask your classmates.

Exchange learning styles.

Have faith in yourself.

Try to make up for what you don't understand.

That's it.

Some simple experiments are done by yourself, such as small hole imaging, plane mirrors (is this to learn?). It's fun.

Mainly cultivate his interest in learning you already have it, oh, yes, yes.

The practice questions should be consolidated and consolidated, and the rest should be looked at the reference books or something, and you will understand.

Increase your interest in physics, do interesting experiments, memorize theorems and formulas, and you will learn physics well.

I feel the same way!!

I may not understand your "always have to spend a lot of time thinking about it slowly", but I have memorized it and I don't understand it very well. But it works out pretty well

That's good. If you want to think clearly, if you don't think clearly, you can do experiments. Physics experiments in junior high school are generally very easy to do.

This is a good phenomenon, read more books, think more, isn't it just to consolidate what you have learned? It's nice to stick with it

That's right, you are an Olympiad material, so you should expand your thinking.

It's better to think about it than to do experiments yourself.

Go your own way and let others say go.

Like to think it's good.

It is suitable for high school competitions.

It seems to be a closed belt because of the nature of the asphalt, and it can be reflective and bright. Therefore, when the light is far away, the light is refracted and reflected, and when it is near, the conditions are not ripe, so it cannot be imaged. This is my personal understanding.

The water vapor on the surface of the earth is a mirage formed by wheels. When the water vapor evaporates on the straight cement road, the water is upward, and it is a reflection of the mirror pants surface, while the asphalt road is relatively rugged, forming a diffuse reflection.

Power = Speed * Resistance.

Set: The resistance of the car during driving is n N.

Power = Speed * Resistance.

n = 90kw 108km h = 5 6 N.

(1)p=f/s=mg/s=1600*10/

2)v=s/t=9000/300=30m/s

Uniform linear motion f resistance = f pull = p v = 90000 30 = 3000n

No matter how it changes, it is inseparable from a formula:

g mm/r^2=m*v^2/r

Gravitational force provides centripetal force, as for the time t taken to fly n laps as mentioned, this is used to find the period, using the period t=2pi*r v, and a slight deformation is sufficient. Do the math yourself, it shouldn't be difficult.

From A to B kinetic energy to gravitational potential energy.

I don't have a picture.

Let the mass of the Sun be m, the gravitational constant be g, the radius of the Earth's orbit r1 = , the radius of Mars orbit r2 = , the Earth's orbital period t1 = 365 day, and the Martian orbital period t2

Then gm r1 2 = (2 t1) 2*r1 gm r2 2 = (2 t2) 2*r2 The left and right sides correspondingly divide by.

r2 3 r1 3 = t2 2 t1 2 so there is t2 = t1*r2* (r1r2) r1 2 = = Earth and Mars are closest to each other again, and the sum of the angles crossed by them is 2 Let t be t, then 2 *t t1 + 2 *t t2 = 2 The solution gives t = t1t2 (t1+t2) = = that is, it will take about years.

When a moving car loses traction, it is also subjected to frictional resistance (which is hindering progress, not power, and running out of power). At this point, the resultant force is backwards, opposite to the direction of motion, so it slows down gradually. But it doesn't stop right away, because any object has inertia at all times.

It was inertia that kept it moving some distance before it stopped. The magnitude of inertia is only related to the mass of the object, and the greater the mass, the greater the inertia. If you are a junior high school student, it is enough to know so much, and you will learn a little deeper in high school in the future.

Please click here, if you don't know it, you can ask again.

1.First of all, the first sentence is wrong, the reason for the motion of the car is not because of friction, friction is what hinders the movement of the car, that is, what slows down the car, if there is no friction, then the car will always maintain a uniform linear motion (Newton's first law).

2.Inertia is a property of an object to maintain its own state of motion, and a property of matter, not a force, the greater the mass of the object, the greater the inertia of the object, and mass is the only physical quantity to measure inertia. The magnitude of inertia is also the magnitude of mass.

This is not true, when you lose traction, you lose momentum. The only force experienced is friction. Inertia is not standing. The magnitude of friction is related to the mass of the car and the friction factor.

The inherent property of all objects of inertia is that they do not change according to external (force) conditions, and they always exist with the object.

Inertia and force are not the same concept, inertia is just a phenomenon. The magnitude of inertia is only related to the weight of the object. A moving car only has friction after losing traction, and you will know it when you are subjected to force analysis, and the existence of force must be acted upon by an object, and if inertia is a force then who is providing that force.

The error is only subject to the frictional force towards the center of the circle, and this frictional force provides the centripetal force.

The gravitational force cancels out the supporting force, and the frictional force is the resultant force, i.e., the centripetal force.

On the contrary, if the frictional force in the tangential direction is also applied, the resultant force of the two frictional forces must not be directed to the center of the circle, and the centripetal force cannot be provided. Got it?

It depends on how the disc rotates, and if it rotates at a constant speed, there is only friction pointing to the center of the circle. In the case of variable speeds, there is also friction in the tangential direction.