If you re not a physics expert, don t enter!!

The key depends on what kind of magnet, and there are two situations:

1. The two ends are heterogeneous magnetic poles, broken from the middle, and their middle is also a heteronymous magnetic pole, which is attraction, such as bar magnets commonly used in physics laboratories;

2. The same position at both ends is the magnetic pole of the same name, the actual situation, for the sake of clarity, we assume that this kind of bar magnet is placed flat on the table, placed left and right, its left end is a different name pole, its right end is also a different name pole, and its left and right ends are the same magnetic poles, and the left and right ends are also the same magnetic poles.

It is equivalent to taking a magnetic pole with a different name at both ends, and when it is placed in front and back on the table, let its length be shortened and its width become longer.

This kind of bar magnet is broken from the middle, and the same position in the middle of them is also the pole of the same name, which is repulsion, and some stationery boxes use this kind of bar magnet.

This kind of bar magnet, when the section rotates 180 degrees, becomes a different name pole, and it will attract.

Theoretically, the magnetic field is generated by an electric current, and the magnetic field of a magnet is produced by the orderly rotation (rotation or rotation around the nucleus) of the charge (electrons) inside the magnet. According to Ampere's rule, when the poles of the same name repel each other, it is an orderly rotation that is a rotation in the opposite direction.

If you close the fractures, it is attracting, and if it is reversed, it is repulsion, because their arrangement is n-s-n-s.

Last time I took a monthly physics exam with 100 questions, I was 99 depressed, and this is the question, and then the teacher explained it to me.

I think you understand.

We set the magnet at the beginning to 1 (left n and right s) and divide it into two (2 on the left and 3 on the right).

When this magnet is split in half.

The left side of 2 is n, so according to the nature of the magnet with two different poles, so the right side must be s, and in the same way, the right side of 3 is s, so the left side is n

So the final sort is ns ns

As for why we don't attract, that's a question of method, and that's theoretical.

Gaga: I'm not a vegetable yet, I'm q33867815

If you think the answer is okay, give it to me.

Because floating. So g wood block = f buoyancy filial piety with lee.

100cm*3=

m=g=mg=

Concentrate. When g is 10 n kg.

Because the exposed volume of the wooden block is 1, sell roll 3

So the density of the oil is.

m=pv=150kg=

1t because Qiaochi 6 cylinders of oil is not enough for 1t

So take 77 barrels.

1, buoyancy is equal to gravity, the gravity formula density multiplied by g multiplied by volume can get 2, g = p wood g * v = p oil g * 1 3 * v = f, the density of oil is so or Xun which 1 ton of oil weight volume is g pxg

Then the total volume of the shirt is used to the volume of Changhong per barrel of oil.

, brought in by f=g gives =1 15

2. Mobile phone! 3.First draw a fixed force, horizontally parallel to 45 degrees, and then there are two forces that are 60 degrees to it, one above and one below, and I forgot the formula for synthesis.

4, blackboard eraser, according to the cow 3 to get gravity equal to friction, so g = f bring in the cow.

Today's junior high school students are really high-end, and they also go online to do their homework.

Theoretical analysis seems unlikely, there should be only one elevation angle to hit the target, but since I want to do it, then I will write down my solution to you:

First, find the initial velocity in both directions, ie.

vx1=vo*cos a1; vx2=vo*cos a2;

vy1=vo*sin a1; vy2=vo*sin a2;

According to the equation of the displacement column in both horizontal and vertical directions, ie.

x=vx*t

y=vy*t+1/2gt^2

So there is x=vo*cos a1*t x=vo*cos a2*t'

y=vo*sin a1*t+1/2gt^2 y=vo*sin a2*t'+1/2gt'^2

This gives us 4 equations, x, y, t, t'Four unknowns, just solve them!

It's purely analytical, don't think about yourself!

The analysis upstairs is basically correct, but the equation has to be slightly modified.

x=vo*cos a1*t x=vo*cos a2*t'

y=vo*sin a1*t-1/2gt^2 y=vo*sin a2*t'-1/2gt'^2

The following two equations should be launched with a minus sign, the elevation angle, and the acceleration in the opposite direction to the initial velocity. However, the solution of this system of equations is very verbose, and you can be tired to die if you type it out in this text mode. Hehe, go back and do the math yourself.

I have a new method, as follows!

According to the kinetic energy theorem, the velocity of hitting the target twice is equal, so there is the following equation:

The square of VO*COS A1 + the square of VY1 = the square of VO*COS A2 + the square of VY2.

In the above equation: the square of vy1 - the square of vo*sin a1 = 2gh (according to the law of linear motion of uniform speed, it is critical).

The square of vy2 - the square of vo*sin a2 = 2gh brings in and solves h

VY1 is the vertical velocity of the target shot at the elevation angle A1) (VY2 is the vertical minute velocity of the target shot at the elevation angle A2) I guarantee that my solution is correct, and it only takes three formulas, and the calculation is much simpler! If you don't believe that the solution and the answer are right, you have to think about it! If you don't understand, I'll tell you slowly!

Solution: It is known that the time for this charge to run in a parallel plate capacitor is t=l v0= s

Let the distance of the particle from the center line ro when the electric field is ejected, then s=1 2at2 (1);

The acceleration of the charge in the electric field a=qe m= (why is there no value of e) is incomplete?

Solution: Let Shenzhou-7 have a mass of m1 and the gravitational acceleration of its orbit is a(h); The mass of the Earth's geostationary satellite is m2, the orbit is at a height of x from the Earth's surface, and its gravitational acceleration is a(x).

The horizontal position of the two points A and C is the same high:

ab = 20 cm, ac = 15 cm, bc = 25 cm, 20 2 + 15 2 = 25 2, that is, ab 2 + ac 2 = bc 2

ABC forms a right-angled triangle with BAC as the right angle and BC as the hypotenuse, and AB is vertically downward.

AB tensile force f1 is equal to the gravitational force g of the weight; BC rally f2 = 0

ab=20cm, ac=15cm, bc=25cm20 2+15 2=25 2, that is, ab 2 + ac 2=bc 2 So abc forms a right-angled triangle with bc as the right-angled side.

AB is vertically downward, so AB tensile force F1 is equal to the gravity g of the heavy object, and BC tensile force F2=0 is mainly force analysis. It's very easy to draw a force diagram.

A, C: Who's on it? How heavy does it weigh?

Is AC on the ceiling? Or on the wall?