1. Physics questions for junior high school. Good 20

I estimate that the gas meter is an instrument to measure the amount of natural gas in your home, which is similar to the energy meter at home, but the structure is different.

1) Q water absorption = cm t = 4200 * 5000 cm3 * 1g cm3 * 10 -3 power * 80 = 1680000j

qput=qm=

Efficiency = 160000J 5600000J = 30 ** yuan.

2) Power consumption: 1000w*30*60=1800000j=,**:yuan.

If natural gas: cheap and versatile; If you choose an induction cooker, it has high thermal efficiency and is environmentally friendly.

1. Endothermy of water: Q=cmδt=

Furnace efficiency = q vq = 30%.

**:Yuan. PS: A gas meter is a gas meter.

2. Power consumption: w=pt=

** is meta. 3. If you choose natural gas: it is cheap and has a wide range of uses.

If you choose an induction cooker: high efficiency and environmental protection.

Choosing C can be a simple move pulley, hanging frame, people are seen as one, and using two moving pulleys is to save one-fourth of the lever, so you only need to divide 1050n by 5, because people have a reaction force when pulling the rope, so it can be considered 1050-x=4x, so x is 210

c, with a hanging basket weight, add weight, and then add a sliding weight, except for a 5, five strands of rope.

1. The quality of each cement block:

m1 = power of the third of v1 = power of the negative two) = 39kg of gravity per block:

g1 = m1g = 39kg 10n kg = 390n2, the tensile force of the cement block to the wire rope is:

The power n of f1 = 20g1 = 20 390n = can be seen from the figure, the movable pulley is borne by 3 sections of rope, so the tensile force of the pulley block on the high-voltage transmission line is:

F2=3F1=3 to the third power n = fourth power n

So the pull force of the pulley block on the high-voltage line is the fourth power n

lz make a picture, and try to calculate the formula yourself.

f A = f B, pressure p A = p B.

If the mass of the liquid in the two containers is equal, then the gravity is equal, and the pressure of the container on the horizontal table is the same, and the bottom area is equal, according to the formula p=f s, the pressure of the two containers on the table top is equal.

It has nothing to do with the density of the liquid, only its mass.

1.On a horizontal ground, pull a trolley with a gravity of 100n with a horizontal tensile force of 50n, so that the trolley advances 5m in the horizontal direction, the work done by the pulling force is equal to 250 J The work done by gravity is equal to 0 J

w pull force = f pull force s pull force = 50 * 5 = 250nm = 250 jw gravity force = f gravity s gravity = 100 * 0 = 0j (displacement in the direction of gravity = 0) 2Pulling a car with a mass of 2000kg on the horizontal road for 400m, doing 3 times 10 to the 5th power, what is the horizontal pull of the horse? (to step).

f=w s=300000 400=750n (mass is used in this problem to confuse people).

m water = 40g

p (density will not hit) water = 1g cm3

v water = m water p water = 40 cm3

v ball = v water = 40 cm3

M-ball = 158g

P-ball = M-ball V-ball =

P iron = p ball p iron hollow.

How simple is the benefit of water Can you find the volume? The density of water is known! Isn't dividing the mass of iron by the volume of water that you find out about the benefits of the paste? Is it right to see the density of the sticker? It's solid, it's not otherwise.

Hollow, because the density of iron multiplied by the volume of iron (the volume of spilled water) is greater than the mass of iron.

The mass of water = total mass - bottle mass = 600g - 100g = 500g is obtained by density = mass volume.

Volume of water = 500g 1g 500cm Volume of water = volume of liquid = 500cm