1. Junior High School Physics Ask for Answers! Finding the value of A is the process!

The easiest way to solve this problem is to look at the electric potential, and think that there is no resistance on the wire, and the electric potential is not reduced, so the lower left, upper and middle are the same as the positive pole of the power supply, which is 14V; The bottom, middle, upper right and the negative pole of the power supply are the same, all of which are 0V.

That is to say, it is 14V before passing through the resistor, and it becomes 0V after passing each resistor, so that you can get the conclusion that the three resistors are connected in parallel more clearly, which is clearer than directly "pulling" the wire, and it is not easy to make mistakes.

a=i1+i2+i3=7+

First of all, this is a parallel circuit with three resistors.

The indication of a is the dry circuit current, so the current i = 14 2 + 14 3 + 14 4 = approx.

This circuit is actually three resistors in parallel, and the ammeter measures the sum of the current of the entire circuit.

The resistance value after the three resistors are connected in parallel is:

r (total) = 2 3 4 = 2*3*4 (2*3+3*4+4*2) = 12 13 (ohms).

So the current is:

i = u/ r = 14/（12/13）= 91/6 a

First of all, look at whether this circuit is connected in series or in parallel, the resistance of the euro is recorded as R2, R3, R4, according to the circuit diagram, we can find that the left end of R2, the upper end of R3, and the left end of R4 can be directly connected to the positive pole of the power supply through the wire (the ammeter can be regarded as a wire), the right end of R2, the lower end of R3, and the right end of R4 can be directly connected to the negative end of the power supply through the wire, so R2, R3, and R4 are connected in series with the power supply, that is, three resistors in parallel, and then find the total current of the circuit = the sum of the current of each branch Quiet.

(1) The mass of the ball: 600*1 12*1=50 grams (2) The volume of the hollow part:

Let the volume of the hollow part be v cubic centimeters.

Then: 3v 4*

Solution: v=350 cubic centimeters.

Both. Stationary and the ship makes a horizontal movement to the left relative to the house.

The flag on the house tells that the wind is from left to right, and the flag on the ship is also in the same direction. It shows that the wind can blow the flag to the right when the ship is stationary, and at the same time, it will not change the direction of the flag if it moves against the wind.

The direction of the wind is to the right. There are three possibilities for the state of movement of a small boat:

1. Still, the same as a house on the shore.

2. Move to the left, the wind blows to the right, and the flag floats to the right.

3. Move to the right, the speed of the boat is less than the wind speed, and the flag is still floating to the right.

1. Relative to the house is stationary.

2. Move to the left relative to the house, and the wind blows to the right.

3. Move to the right relative to the house, and the speed of movement is less than the wind speed (the wind blows to the right).

.The previous ones have pretty much explained the reason. I don't have much more to say.

The house is known to the right of the wind.

The boat runs to the left and the boat does not move.

The boat went right, but it was not as windy as it was.

The house is stationary and the flag is fluttering to the right, indicating that the wind is blowing to the right.

The ship's flag is also to the right, indicating that the air is moving to the right with respect to the ship, and there are three possibilities for the ship's movement:

1.The boat is stationary, and like the house, the air moves to the right relative to the ship.

2.The boat moves to the left and the air moves to the right relative to the boat.

3.The boat moves to the right, but the speed is slower than the wind, and the air moves to the right relative to the boat.

1. G takes 10, w = fs = joules.

2. The filament is directly sublimated into gas, and when it hits the wall of the bulb, it is directly solidified into a solid by the gas, so it is condensation.

3. Inside, it should be that there are many people in the car with high temperature, and the temperature of the window glass is low, when the water vapor with high temperature in the car meets the low temperature glass, it should be released and become water droplets, and the temperature outside the window should be lower than the window glass, but it should absorb heat, so there will be no water droplets outside the window.

1. W FS 20kg x 10N kg x 10m=200J2, the filament that has been used for a long time becomes thinner, which is changed from a solid state to a gaseous state, so it is sublimation (you didn't ask about this, but it is related to what you asked, so I said it); When the gaseous tungsten meets the glass with a low temperature, the solid tungsten that is directly turned into heat release adheres to the glass, so it is condensation.

3. Inside. Because the water vapor liquefies into small water droplets, it needs to be exothermic, and the temperature inside the car is high, and the temperature outside the car is low, only when the warm water vapor in the car touches the cold glass, it can be exothermic and liquefied into small water droplets.

1 According to w=fs w=joules.

2. The tungsten filament is sublimated into a gaseous state by heating, and condenses from the gaseous state to a solid state when it is cold on the inside of the lamp glass.

3. Water vapor comes from the exhalation of the person in the car, the temperature of the glass window is lower than that of the air in the car, and the water vapor in the air meets the cold glass exothermic liquefaction into water droplets, which adhere to the inside of the car glass.

Outside, this small droplet is attached to the outside. It's cold on the outside, it's hot on the inside.

Energy foci empty conservation liquid destruction law: sand)) (

j(sand)=m*r*r=

Get m=15g, so make a fuss t=15s

It's a complicated ......

Let's start with the physical process.

First of all, the small wooden block has a tendency to move to the right under the action of force f. Small wooden blocks are subjected to friction f= n=Ox) <10 (Ox).

So it will be pulled, and the acceleration is (10-4) 2=3 (meter second 2).

At the same time, because the friction force of the flatbed car on the small wooden block is to the left, and the reaction force of the small wooden block to the flatbed is to the right, the flatbed car will make a uniform acceleration movement, and the acceleration is 4 8 = meters and seconds 2), and finally the wooden block will fall down after the relative movement of the car in meters.

1. To do work by tensile force, it is necessary to find the displacement of the wooden block in the direction of tensile force, which is the key to this problem.

If, we choose the car as the frame of reference, then the motion state of the small wooden block is that the initial velocity is 0, the acceleration is meters (2), the displacement is meters, and the motion time is obtained.

at^2/2

t=1 (sec).

Then the displacement of the car is s=v0t in a relatively smooth horizontal plane

at^2/2=0t

3*t*t2=m).

Then the displacement of the force wood block in a relatively smooth horizontal plane is.

m) then the force f does the work w = fs = 10 * joules).

2. To calculate the heat generated by friction, it cannot be calculated simply by the work done by friction, because the work done by friction is first generated heat, and the second is converted into the kinetic energy of the flat car.

But the kinetic energy of the block of wood and the car is the result of the work done by force f, we know the work done by force f, if the kinetic energy of the block and the car can be found, then the part lost, according to the conservation of energy, is frictional heat generation.

The final velocity of the car is meters and seconds, and the kinetic energy e car = 8 * joules).

The velocity at the end of the block is 3 m s, and the kinetic energy e wood = 2 * 3 * 3 2 = 9 (joules).

So heat generation = coke)

[Draw fast and pitch high] indicates that the speed is fast, the frequency is high, and the object vibrates quickly, so the pitch is high.

On the other hand, [low pitch when stroked slowly] indicates that the speed is slow, the frequency is low, and the object vibrates slowly, so the pitch is low.

When the wooden comb teeth vibrate fast, the sound frequency generated will be fast, and the pitch will be high; When you vibrate slowly, you produce a slower frequency of sound, and the pitch is lower, so it affects the pitch

The resistance is p=2000n

The traction force of the front of the locomotive to the carriage is constant f=6000N

f (resultant external force) = f-p = 6000n-2000n = 4000nw (work done by external force) = f (combined external force) * x (distance) = 4000n * 50m = 200000j

After decoupling. The carriage is only subjected to the effect of resistance.

According to the conservation of energy, the work done by the combined external force is eventually converted into the work done by friction.

w (work done by external force) = p (resistance) * x2;

The solution is x2=100m;

Set the mass of the carriage to Y

Then, the acceleration is (6000-2000) y=4000 y, according to v square = 2ax, the speed after driving 50m is v = 200 times the root number (10 y).

The acceleration after decoupling is 2000 y

Then, according to V square = 2ax, the glide distance x2 = 100m

f*x=p*(x+x2)

Using the above equation, the work done by power is eventually converted into friction work.

The speed of the carriage at the time of uncoupling is V

According to the kinetic energy theorem:

f + f）*x=mv^2/2;

After decoupling, according to the kinetic energy theorem.

f*x2=mv^2/2

Solution; x2=4x1=200m

2700kg/m³；Equal; Independent.

The second question is that I made a mistake, right?

Equal; Independent.

Volume v=.9*10 3 1*10 3=9cm3, mass, m=135g=v=mp=135

A student picked up a small stone, measured the mass with a balance of 27g, put it in a graduated cylinder filled with 80ml of water, the water rose to 90ml, the density of this rock is, the density of the size of the two rocks is --- equal, this is because the density of the substance has nothing to do with mass and volume - ---

After the graduated cylinder is filled with water, the volume of water is 250ml from the scale of the graduated cylinder, and the measuring cylinder filled with water is placed on the balance, and the mass is 750g, how many kg is the mass of the measuring cylinder?

The density of ice is, what is the mass of a piece of ice with a volume of 10cm after melting into water - 9 grams? What is the volume of 9cm, 135g of water after freezing, what is the mass? The volume is 150cm