How to learn physics well in junior high school solving

Listen well in class, take good notes, and if you don't understand anything, you must ask the teacher after class.

It's not very difficult to start teaching physics, but it's all basic, and you have to lay it well.

You can find some questions to do appropriately, and if you don't know it, you can also ask the teacher.

You can usually go to the Internet to read about physics, and sometimes there are unexpected gains.

When you first studied physics, you were talking about speed, right?

I must be able to understand it, but I may not understand what to learn, this is normal, speed is the basis of mechanics, just go step by step.

Junior high school physics is very simple.

To tell you, at first, I also found it difficult, it is possible that you, like me, had a fear of him in your heart from the beginning. As long as you listen carefully to what the teacher says, take notes carefully, memorize notes, read the wrong questions before the exam, and ensure that what you miss is no longer wrong, you will definitely get a good score in the exam.

Take your time, in fact, junior high school physics is not too difficult, but some things are difficult to understand. At first, it was to learn the phenomenon of sound, then the phenomenon of light, and there was no difficulty, but when it came to electricity, pressure, and buoyancy, it was a little difficult. I'm a physics teacher, can you ask me any questions!.

Explain your identity when you add it!

Pull an object with a mass of 80kg stationary on the horizontal ground with a horizontal tensile force of 12n, the object is still stationary, the frictional force experienced by the object at this time is 12n, the object is stationary, so it is subject to the equilibrium force, and the pulling force and the friction force in the horizontal direction are balanced, equal, so it is 12n, which has nothing to do with the gravitational force in the vertical direction.

If the object is pulled with a horizontal tension of 160N, the object will move in a straight line at a uniform speed on the ground, and the frictional force on the object is 160N and the net force is 0N. The tensile force in the horizontal direction is balanced with the frictional force, so the frictional force is 160n, and the net force of the object in the resting state and the uniform linear state (i.e., the equilibrium state) is 0, otherwise the object cannot do uniform linear motion or stationary.

12n Because the object is at rest and is in equilibrium, there are only two forces in the horizontal direction, the pulling force and the frictional force, and only if they are equal, the object can be balanced in the horizontal direction.

160n Since a straight line with a constant velocity is in equilibrium, the force experienced is still a balancing force, so the pulling force is equal to the frictional force. The resultant force of the equilibrium force is 0

The frictional force is 12n Since the resultant force exerted on the object at rest is 0, a force of equal magnitude and opposite direction is required to counteract the pulling force.

The frictional force of 160n is 0 because it is a straight line with a uniform velocity, so the net force of the object is 0, Newton's first law.

Analysis: Being at rest on a horizontal ground means that it is only supported by gravity and 2 forces are balanced in the vertical direction, and the gravity is 800n and then the force of 12n is pulled horizontally, and the object is at rest, which means that it is also receiving a balancing force, a balance of tension and friction, because Newton's laws say that an object is at rest or in a straight line at a constant speed when it is not subjected to a force and is subject to an equilibrium force, so it is a frictional force of 12n and the direction of the force is the opposite of the pulling force.

In the same way, the horizontal tensile force of 160n is used to do the motion of a straight line with a uniform velocity, which means that the resultant force is 0, and the frictional force is as large as the tensile force, and the direction is opposite

1 In the circuit of a metal wire, the orientation of free electrons forms the current, the voltage is the cause of the current, and the resistance is the conductor's obstruction of the current.

2 Only the washing machine and the electric oven are working in the home circuit, and the current through them is measured respectively. And the main circuit current of the circuit is 220 V at both ends of the washing machine and 220 V at both ends of the electric oven.

Because the internal resistance of the battery increases, the output voltage decreases.

4.There is no answer.

1. Directional movement of potential difference resistance.

2. 220 220 (Isn't this question a bit .......)3. A (The button battery of the electronic meter is 3V voltage; After the dry battery is used for a period of time, it is not the voltage that changes, but the internal resistance).

4. Isn't this question correct? There is no wrong ......

These questions seem to be junior high school content, right? ......It was a long time ago, and I forgot about ......

1: Move the voltage resistor in a directional direction.

3:d (the output voltage drops due to the increase of internal resistance after the dry battery is used).

4:d (if there is current in the circuit, the voltage cannot be equal everywhere).

The first question, directional movement, directional movement of free electrons, electrical resistance. Question 2, Question 3, DFourth, the answers are obviously all correct, if you don't make a mistake, there are no options in this question that match the meaning of the question. Hope it helps.

Upstairs is not detailed, after my calculations it is true that the initial temperature of the water is 28

Because A and B are both copper, and they are of equal quality.

Therefore, according to the formula q=c m t, it can be seen that the temperature of A and B after boiling water for a considerable period of time is the same, both of which are 100 degrees.

And because A and B are respectively put into the same kind of liquid, the specific heat capacity of the liquid is the same, so the heat absorption capacity is the same.

When A is put into the liquid, the temperature of the liquid is 40 degrees, because the heat is balanced, so A is also 40 degrees, then A puts 60 degrees (100 degrees minus 40 degrees) of heat to the liquid.

When B is put into the liquid, the temperature of the liquid is 50 degrees, because the heat is balanced, so B is also 50 degrees, then B puts 50 degrees of heat (obtained by subtracting 50 degrees from 100 degrees) to the liquid, and the temperature of the liquid is increased by 10 degrees (obtained by subtracting 40 degrees from 50 degrees).

Because the heat absorption capacity of the liquid is the same, the proportion of heat energy absorbed by the liquid is the same, taking B as an example: the liquid gets 50 degrees of heat energy, and it is increased by 10 degrees, indicating that the liquid only absorbs 1/5 of the heat energy given by B.

To sum up the above.

After A puts in the liquid, A gives the liquid 60 degrees of heat energy, and the liquid only absorbs 1/5, that is, after A puts in the liquid, the liquid rises by 12 degrees. Let the initial temperature of the liquid be x

Column equation: x+12+10=50, the solution is 28

If you don't understand, just send me a message, I've added you as a friend.

After boiling two copper blocks of equal mass A and B in boiling water for a considerable period of time, both copper blocks are 100

When the second copper block is inserted, the water changes from 40 to 50

The copper bar drops by 50 and the water rises by 10

The first copper block is put in and it is lowered by 60, then the water rises by 12 and the initial temperature of the water is 28

c copper m * 60 = c water m (40-t).

C copper m * 50 = c water m * 10

Divide by two formulas, t=28

1 formula forgot, trouble downstairs to continue.

2. Use the skateboard as a mat, because the skateboard area is large, the pressure is small, and it will not sink.

3 The density of water is 1, the mass of the metal is 500 grams, the volume is the same, p water: p metal = m water: m metal = 2: 5, the density is.

4. The density of water is greater than that of ice, and the volume of ice is greater than that of water under the same mass, so the glass is broken.

5 Mercury density forgot, trouble downstairs to continue...

1.Because p=fv, f=p v=100000w 10m s=10000n

The same goes for p'=f'v'=3500n*

Pay attention to unit conversion).

5.Because P= Hg gh, H = P Hg = 16000Pa

Solution: Let the speed of the sound in the rail be x

730m/x+2s）*340m/s=730m

The solution is x=4964m s

Let the speed of sound on the rails be V

According to the title: t rail - t air = 2

So there is: (730 340)—(730 v)=2 to solve the equation to get v=4964m s

v=340m/s

Known: t=2s

s=730m

Find: v=?Solution: t is divided by: v=s

Get: v = t of s

4964m/s

1）.The balancing force on the fixed pulley is independent of the direction.

1）.Imbalance; Left; Reduce the force of the balance nut at the right end relative to the fulcrum.

2）.2 pcs.; Cavity Zheng shouted 1n; Greater than.

2）.The volume of liquid discharged.

3）.The pressure of the liquid.

4）.with

Both sets are enthusiastic netizens and answers, I hope to help you, and hope at the same time.

1.Hidden Purity 3 108

Meter seconds. 2.Vacuum parlor 3 4 2 3