Those who know physics will enter, and those who will be physical will enter

Forget it, then I'll keep it simple.

1 No, it will be a handstand and zoom image, because the image on the outside exceeds the focal length of the convex lens by 2 times.

2 big ones, for example, oh: if you use a small gear to watch a turn, that wheel may turn half a turn, and when you use a big wheel to watch a circle, the wheel may turn 2 times, you compare it yourself.

3"White gas"Floating downward, because white gas is countless small droplets, heavier than air, so it floats downward.

4. The density of clear water is relatively small, and the density of eggs is greater than that of clear water, so it will sink, but when salt is added, it becomes salt water, and the density of salt water is greater than that of eggs, so the eggs float.

5 Thermal expansion and contraction, when it is hot, it expands empty, and when the temperature drops on the balloon, the volume of air shrinks, so it is"Suction"Lived the balloons.

Is it clear?

Hey, let your physics teacher tell you slowly

A good student who loves to ask questions is a good student. You're a seedling!

I'll just say two

Question (4), because the density of brine is greater than that of clear water, and it is also greater than the density of eggs.

Question (5) is because the volume shrinks when the air temperature drops.

Hehe, the rest is up to you to find out for yourself!

It would be useful to read more extracurricular books.

This is my experience.

Hope it works for you.

1) It's a convex lens.

2) Of course, it's big, so it's the same as the previous one, and if it's small, you have to pull some force in front.

3) The density is less than that of air

4) Salt water is denser than water

5) Air pressure difference.

1. The magnifying glass will refract the light, and the light that was originally flat will be expanded. When you look at it, you feel big. The window pane does not refract and does not affect.

2 large, the more the gear hits, the more labor-saving, because of the principle of leverage. The longer the rod, the less effort it takes, and the gear is just a number of levers.

3. Air conditioning is due to the condensation of water in the air into small droplets.

4. The higher the density of the liquid, the greater the buoyancy, and the greater the buoyancy of adding salt.

5. When the air becomes colder, the pressure becomes smaller, and the pressure inside and outside are equal, but the inside becomes smaller and the outside remains the same, so the cup is pressed instead of sucked.

1. No, reason; Practice.

2. Small, this is the cause of the work and torque.

3. The air near the popsicle should be liquefied from high to low, and the naked eye can observe an upward trend.

4. First of all, it is necessary to understand that the object in the water has buoyancy, and adding salt increases the density of the aqueous solution.

As a result, the buoyancy increases, and the upward shot rises.

5 This is the air pressure, the hot cup will cool down, and the gas in the cup will also cool down, resulting in a decrease in air pressure (this is the principle when you suck milk), so the atmospheric pressure will press the balloon on the cup, and it becomes sucking.

The upper body continues to move forward at the same speed, and the movement of the feet changes.

Too much ......I don't want to talk about ......2,4,5 are just ...... to spark interestLearn ...... later

It is based on this theory: (the melting point of a substance decreases as the pressure increases).

The pressure on the part of the ice that comes into contact with the wire is stronger than the atmospheric pressure, and the melting point of the substance increases with the pressure, so the ice under the wire will melt into water, so that the wire will sink a little, and the melted water will be in the upper part of the wire, and because the pressure is only atmospheric pressure and the temperature at that time is below O, it freezes here. In this way, the wire gradually sinks until it passes through.

In figure skating, this is the case, the skate blade is very thin, and the pressure acting on the ice surface is very high, so the ice dissolves into water where the skate passes through and immediately freezes, thus leaving a white mark.

Answer: Because the freezing point of alcohol is low, the freezing point of the internal combustion engine cooling water will be reduced by adding alcohol, so that the cooling water is not easy to freeze and solidify.

Choose C "its power supply is very hot, and even can smell a strong rubber smell" This sentence shows that the wire is very hot, because the wire and the water heater are connected in series, and the current in each place of the series circuit is the same, and the greater the resistance, the hotter it is, so it means that the wire resistance is large.

If A is selected (the wire is too short), the shorter the wire, the smaller the resistance, according to the resistance r=p*l s. In this way, the wire resistance is small, and it cannot be a (if you don't use a formula, common sense is like this).

If B is selected (the wire is too thick), the thicker the wire, the smaller the resistance, according to the resistance r=p*l s. In the same way, the resistance of the wire is small, and it is impossible to b

If C is selected (the wire is too thin), the thinner the wire is, the greater the resistance according to the resistance r=p*l s. In this way, the wire resistance will become larger, and the higher the resistance, the hotter it will be, so C is okay.

If D is selected (the voltage is too high), it is possible according to the formula, but the household circuit is constant 220V, which will not be high.

The power supply is so hot that you can even smell a strong smell of rubber.

It means that the electrical power of the energized wire is too large, and the wire can be seen to be a fixed resistance p=U2 r

r=pl/s

u=ru total r total.

Therefore, the A wire is too short and the B wire is too thick, so the resistance is small, and the electrical power becomes smaller when the total voltage is not the same.

c。If the wire is too thin, the same goes for the electrical power to become larger.

If the D voltage is too high, you can also choose CD (but the voltage in real life is generally unchanged).

Select AB power p=u*i=u*u r

Resistance r=p*l s

Therefore, the power p=u*u*s (p*l).

The power supply is too hot, so the power is too large, and the voltage U is a constant of 220V, so there is S too large to conform to the topic or L is too short, so AB is selected

Let the angle between the wooden board and the floor of the hall forest be sin = 1 5

fn=gcos=1000*root:24 5=400,root:6

F push car volt answer = f = fn + gsin = root number 6 + 1000 * 1 closed wisdom 5 = 240 root number 6 + 200

200+240√6）n

Draw a force analysis diagram, the thrust should be balanced with the force of the glide force and the friction force...

Solution: According to the analysis of the problem, there are two forces to do lagong, i.e. g f

by wg=mgh wf=umgl

100 * sin37 * = * 100 * 882j =

The external force is only the supporting force of the inclined plane.

The work done by the supporting force: w=mg * sin37 * l100*

1176j

The work done by gravity: w weight = gh = mglsin 37 ° =

Friction w friction = fl= nl= (gsin37°)l= (mgsin37°)l=

(1) The maximum speed of the car when driving along the horizontal highway at a constant speed, at this time, the traction force is equal to the resistance p=fv=fv

The maximum speed of the car along a horizontal highway is v=

2) Set the car to accelerate from a standstill, by the ox two.

f-f=ma

The traction force f= is solved

When the uniform acceleration speed is maximum, p=fv

The maximum velocity of the solution is evenly accelerated, v=

The time that can be maintained by the uniform acceleration motion of the car is obtained by v=at

I didn't give any points, I can only say one idea: p=fv; vt squared = 2as; s=v0t+1 2at squared.

(1): According to the formula p=fv....Then to make the maximum speed f, the minimum is the resistance f=6000*10*, then vmax=30m s can be obtained

2): According to the acceleration formula ma=f(result), f(result) = 30000N....And because f(combined) = f-f....

So we can get the critical state of f = 30000 + 3000 = 33000n ....According to the formula p=fv, v=30 11m s....The maximum speed was obtained.

I also know that the acceleration is 5m s....Then we can know that the uniform acceleration time is 30 11 divided by 5 to get t = 6 11s....

q＝cm△t

A and B get the same amount of heat, both are c water m water t

tA, tB.

tA, tB.

C A C B.

<> Block M is placed on an inclined plane, when from small to large, Block M will slide when Tan = At this time, mgsin = mgcos -mgsin mgcos = tan , block M does not slide at a uniform speed,-- defines Bodan as between the block and the inclined planeMaximum coefficient of static friction。When mgsin > mgcos, the coefficient of static friction becomesCoefficient of dynamic friction'。In general'Sometimes it is taken for computational convenience'= Hidden Silver.

When AB enters Yuyou, the effective length is AB length, and when ABCD both enters, the effective length is 0, because the magnetic flux does not change (the magnetic field of the ballast pin is constant).