Find several types of junior high school physics calculation problems

According to the pressure of the liquid from the formula p=h g, it is known: liquor = kilogram cubic meters. Mercury = kilogram cubic meter. A standard atmospheric pressure p = 760mm mercury column, find: h wine.

Solution: P large = h wine wine g, p large = h mercury mercury gh wine wine g = h mercury mercury g

H wine = h mercury mercury wine.

The value of 1 standard atmosphere is 760 mm of mercury, which is the height of the meter mercury column.

Solution: The mercury pressure is known to be p=

Alcohol pressure p alcohol =

p = p alcohol.

Establish. The height of the mercury column is: HS

The alcohol column height is: HJ

hj/hs=jp/hp

hj : m = :

hj : = :

hj = =

The height of the alcohol column is meters.

Summary. 1) Switch S1 S2 is in a closed state, because the hair dryer needs to be heated during normal operation, and the heating needs to pass through the heating wire, and the heating wire needs to be energized, so the switch S S must be in a closed state to make the hair dryer work normally. (2) The electrical power of the wind power heat wire is p = UI = 220V1A = 220W.

3) When the motor blows hot air normally, the rated power is 50W, and the working time is 484S, then the electric energy consumed by the motor is E = PT = 50W484S = 24200J. At the same time, the heat generated by the electric motor is also 24200J.

Hello, I would like to ask about the question in **, I will see if it will be done.

It's very blurry, big brother, so you typed it, I can't see it clearly.

Do only one question, which question you choose.

Which one you can see clearly and do that.

I can't see any of them.,You see this pixel is a mosaic, brother.。

The first question is whether you can shoot clearly.

The detailed steps are shown in the figure above.

Uh-huh, excuse me.

1) Switch S1 S2 is in a closed state, because the hair dryer needs to be heated during normal work, and the heating needs to pass through the heating wire, and the heating wire needs to be energized, so the switch S S must be in a closed state to make the hair dryer crack and let the wind work normally. (2) The electrical power of the wind power heat wire is p = UI = 220V1A = 220W. (3) Under the condition of normal hot air blowing of the motor, the rated power is 50W, and the parallel operation time of the workshop is 484S, the electric energy consumed by the motor is E = PT = 50W484S = 24200J.

At the same time, the heat generated by the electric motor is also 24200J.

S1, S2 closed.

It's really hard to say on the Internet, so it's better to find your teacher or find a piece of information, there are specific questions to ask.

The pulley principle is:

Roughness causes friction between the joint and the object.

Thus creating frictional force.

Smoothness makes the two objects not produce friction.

g=1 2 How to draw a picture, you will know most of the drawing problems.

In addition, you can go to the physics network to find questions.

15.The "Seagull 300" light amphibious aircraft designed by the Sixth and Fifth Research Institute of the Aviation Industry will make its first flight in October this year, and the aircraft can carry 4-6 passengers, is equipped with high-performance engines and advanced aviation instrumentation equipment, and can be used for business flights, cargo transportation, coastal patrol, and so on. The total mass of the aircraft is 4000kg, and g is taken as 10N kg.

1) When the plane is parked on the water, what is the volume of water discharged?

2) If the aircraft flies at a constant horizontal speed of 360km h in the air, the resistance it receives in the horizontal direction is times the gravity of the aircraft, what is the power of the aircraft engine?

1) When the plane is parked on the water, i.e. (1 point).

So: (1 point).

2) When the aircraft flies at a constant horizontal speed, the power is equal to the drag, i.e.:

f (1 point) The power of the aircraft.

1 point).

Fixed value resistors R1>R2, if they are connected in a certain way, connected to the power supply, the power of R1 is 16 watts, and the voltage at both ends of R2 is 8V, if they are connected in another way, and then connected to the same power supply, the power of R2 is 100 watts, find: (1) power supply voltage U; (2) The resistance value of the resistor r1.

I didn't find a difficult calculation question, so I'll give you a multiple-choice question first:

If a mass of iron and water absorb the same amount of heat and put iron into the water, then a: heat is transferred from iron to water.

b: Heat is transferred from water to iron.

c: There is no heat transfer between iron and water.

D: Can't tell.

Select d (the initial temperature of water and iron is not controlled).

A streamlined car that maintains an acceleration motion in high-speed running, then whether the car is drifting or gripping.

(1) It will not melt; The rice cooker can only be kept warm, and the temperature of the food in the rice cooker should not exceed 80; S2 is an automatic temperature control switch, which will automatically disconnect when the food temperature in the pot reaches 80, and will automatically close when the temperature is lower than 70, without overheating.

2) The ratio of electric power consumed to heat and keep warm rice cookers:

pHeating pKeep warm = u2 r1) [u2 (r1 r2)] r1 r2) r1

The amount of heat that must be absorbed by boiling water at a standard atmospheric pressure is:

q suction =cm(t - t0)=

p heating = u2 r1 = (220v)2

Q discharge = p heating t = 1000w 1000s = 106j efficiency of conversion of electrical energy into internal energy = q suction q suction = 106j = 84%.

1.Of course not, 103 S1 will automatically disconnect the aluminum pot and will not melt, S2 is an automatic temperature control switch, it will automatically disconnect when the food temperature in the pot reaches 80, and it will automatically close when the temperature is lower than 70, without overheating.

The square division R1 + R2 is heat preservation, and the U square division R1 is heating, and the substitution value is good.

.Gasoline produces heat.

q=q*m=,000,000

55,200,000j

p=q/t=92000w

2. Traction does the work.

w=fs14400000j

p=w/t=v*t=24000w

Solution: (1) The heat released by the complete combustion of gasoline: Q = Qm = The power consumed by the car: P1 = Q t = =

2) The distance that the car passes within 10min s=vt=20m s 600s=the work done by the car's traction force within 10min:

w=fs=power of the work done by the traction force of the car:

p2=w/t=

1) The rice cooker can only be kept warm, and the temperature of the food in the rice cooker should not exceed 80

2) At 1 standard atmosphere, the boiling point of water is 100, so the S1 automatic power-off and rock deficit function does not work.

3) Ratio of electrical power consumed to heat and keep warm rice cooker:

pHeating pKeep warm = u2 r1) [u2 (r1 r2)] r1 r2) r1

4) The amount of heat that must be absorbed when boiling water at a standard atmospheric pressure is missing

q suction =cm(t - t0)=

So q put = q suck 84% =106j by q put = u 2t r 1:

Displacement (buoyancy) = the weight of the ship itself + the weight of the cargo when fully loaded (gravity = buoyancy). Displacement is usually expressed in tonnage, and the so-called displacement tonnage is the tonnage of water discharged by the ship in the water, and it is also the tonnage of the ship's own mass.