In the second year of junior high school, physics can answer as much as you can, and if you answer a

1. Disappearance; Superconductor.

2. Voltage; Voltage; positive charge; Negatively charged; Voltage; Voltage;

4. The total resistance caused by the parallel connection of multiple electrical appliances is too small, and it can be seen from the formula i=u r that when the voltage is unchanged, the smaller the resistance, the greater the current generated, so connecting too many electrical appliances will cause the current to be too large, and then cause tripping.

6. The actual power of the electrical appliance can be changed by adjusting the resistance; Electric current does work.

7. Electricity; other forms; Different forms can be transformed into each other.

8. Electricity; Machine; The energized conductor rotates under force in a magnetic field; Electric fans, range hoods.

9. There is a magnetic field around the energized straight wire.

10. The energized wire will be subjected to force in the magnetic field; Electricity; Machine; Current commutators, rotors (coils), stators (permanent magnets), DC power supplies.

11. a magnetic field; tangent; Balance; Balance; Inertia; current direction; Current commutators.

12. an earpiece; Microwave.

13. an electromagnetic wave; Electromagnetic wave; Electromagnetic wave;

14. a digital signal; Signal; Digital signals.

1.Disappear superconductors.

2.Directional movement of free electrons Voltage Positive charge Negative charge Potential difference Magnitude of voltage.

Thermal effect of electric current.

6.The voltage does not change, and the current magnitude affects the speed of the work done by the current.

7.Electrical energy Other forms The process by which electrical energy is converted into other forms of energy.

8.The electrical mechanical energized coil in the magnetic field will turn the fan of the washing machine9Magnetic effect of electric current.

10.The energized coil turns in a magnetic field electrical mechanical (forget later.)

11.The magnetic field turns.

1. Equal to 0 superconductor.

2. Directional movement of electric energy, positive charge, negative charge, voltage, voltage.

4. The thermal effect of electric current.

6. Electric power The speed of the work done by the current.

7. Other forms of electricity.

8. Electromechanical energized conductors are stressed in a magnetic field.

9. The magnetic effect of electric current.

10. An energized conductor is subjected to a magnetic field by an electrical machinery.

11. Magnetic field, motion, balance, balance, inertia, current direction, commutator.

12. Earpiece electricity.

13. Electromagnetic waves: Electromagnetic waves.

14. Digital signal, electrical signal, digital signal.

1 Disappear Superconductor 2 Voltage Voltage Positive Charge Negative Charge Voltage Voltage Let's do it first, there's no time.

First find out the rough focal length of the magnifying glass, the method is as follows, put the magnifying glass in the sun, and move up and down, find out the smallest spot, use a scale to measure the distance between the spot and the magnifying glass, this distance is the focal length; All right. Next, let's analyze the magnifying glass, the magnifying glass is a convex lens, and the imaging law of the object from near to far is: it becomes an upright magnified virtual image within a double focal length; Between one and two times the focal length, it becomes an inverted magnified real image; A real image that is turned out in an inverted handstand outside twice the focal length.

Summary: One time the focal length is divided into virtual and real, and two times the focal length is divided into size, when it is greater than one time of the focal length, the object near the real image and the far image become larger.

Place a magnifying glass on top of the object, adjust the distance between the magnifying glass and the object, and you can see a virtual image (magnified, upright) through the magnifying glass.

Convex lens imaging experiment Find your own textbook.

Not always magnified, magnifying glass is equivalent to a convex lens, if you think of it as a convex lens, then:

The resulting image is as follows: an upright magnified virtual image within a double focal length.

Between one and two times the focal length, it becomes an inverted magnified real image;

A real image that is turned out in an inverted handstand outside twice the focal length.

1. Suddenly it becomes 0. Superconductor.

2. Voltage; Voltage; positive charge; Negatively charged; Voltage; Voltage;

4. Overload (too much power, resulting in excessive current, exceeding the bearing capacity of the fuse or air switch.) ）

6. The electric power is different. Apply work.

7. Electricity; other forms; Electrical energy is converted into other forms of energy.

8. Electricity; Move. The electric current is acted upon by force in a magnetic field. Fan. Air conditioning.

9. The energized wire can generate a magnetic field.

10. The energized wire is subjected to force in the magnetic field. Electricity; Move. Magnetic pole. Coil. Brushes. Commutator.

11. a magnetic field; Turn. Vertical. is 0. Neutral or balanced. Inertia; current direction; Commutator.

12. an earpiece; Digit.

13. Radio waves. Radio wave. Radio wave.

14. Analog signal. Digital signals. Digital signals.

1.Suddenly disappear superconductors.

2.Directional movement of electric energy Positive charge Negative charge Voltage voltage.

Coulomb 4The more parallel resistors, the smaller the total resistance, and the greater the total current when the voltage is constant.

5.Zero, zero.

6.The current in the conductor is related to the resistance of the conductor when the voltage is the same and the current does work.

7.Electrical energy Other forms Electrical energy is converted into other forms of energy.

8.Electrical-mechanical energized wires are subjected to a force in a magnetic field of electric fan washing machine.

9.An energized spool is the presence of a magnetic field.

10.Energized wires are subjected to force in a magnetic field Electromechanical stator rotor coil commutator.

11.Magnetic field rotation vertical balance balance inertia current direction commutator.

12.Earpiece electromagnetic waves.

13.Electromagnetic Waves Antennas Electromagnetic waves.

14.Digital Signals, Analog Signals, Digital Signals.

4.Overcurrent protection.

7.Electrical energy in other forms of energy conversion.

12.Handset Numbers.

1. Become 0, superconductor.

2. Voltage, electromotive force, positive charge, negative, voltage, voltage.

Hello. The action of force is reciprocal, it reveals the relationship between the force and the force, and it is necessary to find out what kind of object the force and force object are in question. As long as an object A has a force on another object B, then A is called a force and B is called a force, but in any case, as long as an object has a force on another object, then another object will also have a strong force on this object, which is called the effect of force is mutual.

For example, in the example you mentioned, the hand has a strong effect on the rope, then the rope opponent also has a reaction force, in this case, we can call the hand the force, the rope is the force, or we can say that the hand is the force, the rope is the force, they are mutual (this is the contact force); Another example is the magnet and the iron (when there is no contact), they are attractive to each other, and they are also mutual, we can say that the magnet is the force object, the iron block is the force object, or we can say that the magnet is the force object, and the iron block is the force object. The key is to see which object it acts on.

I don't know if it's written clearly, but if you don't understand, you can ask me.

The hand is applied to the rope, and the force between the hand and the rope is mutual.

The rope is applied to the barrel, and the force between the rope and the barrel is mutual.

The action of force is mutual, so the force object is also the force object, in a specific event, to determine who is the force object, who is the force object, it depends on the study.

For example, in the previous phenomenon, the reason why the hand feels pain is because the rope is exerted by the opponent, the rope is the object of force, and the hand is the object of force.

The rope at the grip of the hand is deformed, and the hand is the force object, and the rope is the force object.

The reason why the barrel rises is that the rope has a strong effect on the barrel, at this time the rope is the force object, and the barrel is the force object.

The action of the force is mutual, and the object applying the force and the object being stressed are not necessarily in contact.

For example, pull a rope by hand to bring a bucket up from a well.

The hand exerts force on the rope: the rope is the object of force, and the person is the object of force.

The rope comes to the bucket, the rope exerts a pull on the bucket, the bucket is stressed, and the rope exerts force.

The hand exerts force to the rope, and the rope exerts force to the bucket, and the rope plays the role of transmitting force.

Need not. It's a rope. Some forces are contact forces, such as frictional elastic force. Some forces are exerted through fields, such as electric field force, magnetic force, gravitational force. Please be encouraged to do the task.

1. The mass of soil is m = density * volume = 1600 * 10 = 16000 kg.

The total mass of soil and trucks is 10,800 kg + 16,000 kg = 26,800 kg.

The total gravity of the soil and the stalking vehicle, that is, the pressure on the ground f=g=mg=26800 kg*10n kg=268000n

If the four wheels of the truck are respected, the force area is s=800cm=so the pressure on the ground p=f=s=268000NPa.

2. The main purpose is to reduce the pressure of the vehicle on the ground, because the iron-laying plate can increase the stress area, and the area in the hand is large, and the pressure of the vehicle on the ground is reduced, which can protect the road surface.

Loading mass = soil density x loading volume slippery = thousand lines of songke.

Truck gravity = truck mass x small g = cow.

Loading gravity = soil mass x small g = cow.

Total pressure = loading gear to let gravity + truck mass =

p=f s=pascal.

The steel plate is to reduce the pressure of the vehicle on the ground, the steel plate can increase the stress area, the contact area is large, the pressure of the vehicle on the ground is reduced, and the road surface can be protected.

Go to Zhang Jing. kg, f truck Lihuai = g = mg = 10800kg 10n kg = 108000n

f soil = g thumem width = mg = vg = 10m m 10n kg = 160000n

s=200cm²×4=800cm²=

p=f s=268000n Phra Limna.

The purpose is to increase the contact area and reduce the pressure.

1. The mass of soil is m = density * body respect sensitive and prudent volume = 1600 * 10 = 16000 kg.

The total mass of soil and trucks is 10,800 kg + 16,000 kg = 26,800 kg.

The total gravity of the soil and the truck, i.e. the pressure on the ground, f=g=mg=26800 kg, Liangjing*10N, kg=268000N

If the truck has four wheels, the force area is s=800cm = so the pressure on the ground p=f s=268000NPa.

2. The main purpose is to reduce the pressure of the vehicle on the ground, because the iron plate can increase the force area, and the pressure is small.

First of all, how many wheels? Count it into four, which is p=f s f=mg=10800x10 s=

The second is obviously to increase the surface area of the finger pin in contact with the soil, reduce the pressure, and prevent the car from sinking into the soil. If you want to calculate, it is the soil that can withstand the pressure of the sun's fun. Then the load gravity is greater than the pressure that the soil can withstand. Therefore, it is necessary to lay a bent steel plate.

It is known that the side length of sugar a=1cm=

The distance between molecules d=10e-9m

Find: the number of molecules n

Solution: Volume of sugar v (sugar) = a * a * a = cubic meter.

The volume v (molecule) occupied by each molecule = d * d * d = 10e-9 * 10e - 9 * 10e - 9 = 1 * 10e - 27 cubic meters.

The number of sugar molecules n=v(sugar) v(molecule)=1*10e-6 1*10e-27=1*10e21.

Answer: The number of molecules is 10 to the 21st power.

It is known that the edge length of the sugar cube is 1cm, and the spacing of sugar molecules is 10 to the minus 9 power, and the meter is equal to 10 to the minus 7th power.

1 divided by 10 to the minus seventh power, and finally in the third power is its number, and finally it is equal to 10 to the 21st power.

I don't know what I want, or I can't type, it's inconvenient to write.

3 Disagree Charge cannot be created out of thin air, cannot disappear out of thin air, matter is conserved, but the charge is transferred.

Why not just search the web.

Known: f=1000n, g1=100n

Qiu Sen's attack on this brother: g thing = ? fResistance=?

Solution: according to f=g+fresistance.

G+FResistance=1000N

According to g+g1=f+f-resistance.

g+100n=1000n+f.

g-f resistance = 900n

So g = 950n f resistance = 50n

The carrying weight is 1000N, and the air resistance is 100N.

The speed at which sound travels through the air is.

340m s, if Xiao Ming hears thunder 2s after seeing lightning, the distance between the thunder and Xiao Ming is.

340m s*2s=680m, 340m s*4s=1360m choose C