Middle School Physics. Expert ask a junior high school physics

1. Pinion. Because the back uses the small one, the front has to use the big one, and the big workmanship skills are bigger than the small ones, so

2. The liquefied small water droplets, downward, because they are small water droplets, heavier than air, so they sink downward.

3. Because the density of brine increases after water is added to salt, it is gradually greater than the density of eggs, so eggs do not sink.

4. Liquefied small water droplets.

5. Because the cup and the air inside are very hot, the pressure is small, and the pressure around it is strong, so the balloon is pressed in.

1 large gear, pinion for acceleration, laborious.

2. Water vapor, the surrounding water vapor condenses into small water droplets when it is cold and heated, and it should go upwards.

3. The density of water after adding salt is greater than that of eggs.

4. Hot air is the heated air, and the hot cup can suck the balloon because: after heating, the air expansion in the cup is reduced, when the balloon plugs the mouth of the cup, the cup is sealed, and the pressure in the cup is less than the pressure in the atmosphere, so the balloon is pressed and buckled.

1.Tooth 2 The popsicle has just come out of the refrigerator and since the air around it is hot, the air condenses into small water droplets that look like gas and of course they are downward, because the small water droplets are definitely denser than the air. 3.

Archimedes' principle The greater the density, the greater the buoyancy The addition of salt increases the density of the water so that the egg does not sink 4 atmospheres.

Large gear wheels in the back and pinions in the front. In this way, the arm of the rear wheel is large. The front is with a pinion because the arm is larger relative to the two tread front gears. In this way, two strong arms are used to drive the tires, which saves effort.

The water vapor in the air liquefies in contact with a cold object, and what you see is not a gas but a small droplet of water like a fog. As the air liquefies, the liquefied air is rapidly evaporated, so what is seen is an uptick.

1.Big Gear (Axle) 2Up (cold air is a bit denser) 3

The density of the water becomes larger after the salting, and the density of the egg is roughly equal to the density of the water, and when the egg is put into the brine, the egg will float. 4.Hot air is hot air.

Heat tension and cold contraction.

The first one on the first floor was wrong, and although I can't say why, anyone who has ever ridden a car with a transmission knows that it is the big gear.

Summary. Dear, is the topic complete?

Dear, is the topic complete?

Complete, what I would like to ask is the first question why buoyancy = gravity.

Pro, the vertical force is balanced in the floating state.

So the upward buoyancy is equal to the downward gravitational force.

No, who doesn't know, shouldn't there be an upward pull when the rope is straightened.

Dear, yes, buoyancy is equal to gravity when there is no rope at first, and gravity is equal to the sum of buoyancy plus rope tension after connecting the rope.

Please explain clearly.

Dear, you can take a look at the answer process.

I didn't see the question clearly, thank you.

The maximum buoyancy is the gravitational force of the water that is dissipated.

p=fv

Float = v=g gp1 The buoyancy is the largest at this time (calculate the result by yourself).

2.Assuming that the height of the outcropping surface is x, then the time taken is x v rope pull force f+f floating'-g=0 f float'= So f=. -vt）

g（h。-h）v

Although this question is about physical phenomena, it is actually a math problem, that is, to test whether you can see the function curve, the abscissa and the ordinate of point A are equal, so the answer is "=" point b abscissa is obviously greater than the ordinate, so the answer is " "There is no need to discuss any force situation, because the force situation is this function curve.

If the question states that the motion of the object is a uniform motion, then, regardless of a or b, when the object is at rest or in a constant motion, the resultant external force is 0, so fa=fa, fb=fb

If the motion of the object is accelerated, fb > fb

If it's a deceleration motion, fb

It must be the choice of B.

Are you a human-taught version of the physics textbook [we are], if so, then on page 7 there is the following original words:

At the beginning of the 20th century, scientists discovered that the structure of the atom is very similar to that of the solar system, its center is the nucleus, and around the nucleus, a certain number of electrons are moving around the nucleus.

Hope it helps, o( ohehe.

I think the answer is D, and the reason is that the ball is floating in B.

It should be b. It's been a long time since I've taken a physics class, and I've almost forgotten all my previous knowledge.