In a hurry, please consult a physics master and ask a physics master for help

I think you should know the following:1. Common force analysis.

2.Common motion analysis (e.g., flat throw, free fall, vertical throw, uniform speed linear motion, etc., some kinematic formulas) 3

Newton's Three Laws. 4.Conservation of momentum, conservation of mechanical energy, geography of kinetic energy.

5。Ampère's law in electromagnetism, energy law, Faraday's law of electromagnetic induction. 6。Understand some of the hallmark discourses of molecular motion (e.g. the average kinetic energy of molecules and what there is).

7。Electricity: Be able to analyze circuits, understand some basic circuit diagrams, and memorize commonly used formulas.

Memorize some frequently used formulas, be proficient in force analysis, and have a strong sense of energy conversion.

I don't think it's enough to rely on a teacher just to do physics.

You're probably going to have to rely on your own understanding.

I suggest that you find all the physics books in high school, and then find the corresponding exercises for each lesson, you don't need too much, you read the textbook carefully first, and then do the corresponding exercises.

When you don't understand, it's best to figure it out by yourself or look up the information by yourself, so that you can just remember it.

After learning the basics, slowly increase the difficulty of the questions.

That's what my physics is.

If you follow my method, I guarantee that you will score above 70 points in physics.

1.Force analysis.

2.Newton's Laws.

3.Conservation of energy.

4.The Law of Circuits.

5.Electric field formula.

All of this is understood, and high scores can be taken.

Assuming that the aluminum ball is solid, then v=m = to the 3rd power) = 3rd power cm3 3x10 to the 3rd power cm3, so the pulse is hollow, the hollow part of the base repentance volume bridge is 3x10 to the 3rd power cm3-2x10 to the 3rd power cm3 = 1000cm3, if filled with water, the volume of water is 1000cm3, then.

m water = v = 1x1000 = 1000g = 1kg, then m total = 1+

1) vc = [(l 2-h 2) 1 2] h va (or vb).1

1/2m(vc^2+2va^2) =mg(h-√3 l）..2 VA(H) and VC(H), A and B are co-accelerated, A=DVA(H) DT = DVA(H) DH DH Dt where H= 3 L + VCDT, DH DT = VC

This gives a value.

2) Calculate the previous question. This question is very simple: vc(h) has been obtained, and dvc(h) dh is derived directly from h, so that dvc(h) dh = 0, and h, i.e., vc(h) is the maximum, =arccos(h l).

The calculation process can be a bit cumbersome, do the math yourself.

Ask the teacher to go, I read it for a long time, and I can't put pen to paper.

First, the force of c is analyzed, and the sum of the velocities of ball b and ball a is added, and then the relationship between h and v is derived by trigonometric functions. The second question has not been done yet.

Did you get your question wrong? [Slide the right end of the board to the left and slide the plank] There seems to be a problem here.

The principle of solving this problem is:

1》Conservation of mechanical energy, that is to say, the two physical energy potential energy and kinetic energy involved here are equal to the initial kinetic energy, that is, 1 2mv2=1 2m(1 2v)2+1 2mv'2, plus the law of conservation of momentum mv=1 2mv+mv'Forming a system of binary linear equations can be used to find the mass ratio.

2》Maximum kinetic energy: The velocity of the board and the iron block is the same when the maximum kinetic energy is the same, that is, the application of the law of conservation of momentum, that is, mv1=(m+m)v2, at this time, v2 can be obtained, and the kinetic energy is found by the kinetic energy formula.

The distance of ball B is 15m, first according to the formula S = use the formula to find the time for ball B to land for the root number 3 seconds, and then add this time to 1s is the total time of ball A landing 1 + root number 3 seconds, and then use the formula S = to find the distance of ball A that is, the height is 20 + 10 times the root number 3.

From h=1 2gt 2, the movement time of the B ball can be obtained from the root number is 3 seconds, and from the title, the movement time of the A ball can be obtained from the title is 1+ the root number 3, and then the distance from h=1 2gt 2 can be obtained as meters.

1. Focus (at one time the focal length) At the double focal length, the image is inverted, and the object and image are located on the opposite side of the lens The image is upright, and the object image is located on the same side of the lens.

2. Place the candle at or within one focal length.

or the center of the three is not at the same height.

Or the object is close to the focal point, and the image is far away, and the light screen cannot be accepted.

1.1 double focal length; double focal length; Handstand; Upright.

2.The reason may be that the distance from the candle to the lens is less than double the focal length.