Scientific problems are urgent, scientific problems are urgent

Answer: b Let the bottom area and volume of the two cubes be s1 and s2 respectively; v1, v2 by, the pressure is the same then f1 s1=f2 s2

f1 = 1·g·v1, f2 = 2·g·v2 1·g·v1 s1 = 2·g·v2 s2, where 1·h1 = 2·h2

From conditions 1> 2 we get h1 h2

where h1,h2 are the cube side lengths.

You can get s1 s2

Joint condition p1=p2

We get f1 s1=f2 s2

i.e. f1 f2

ρ1*v1*g)(l1*l1)=9ρ2*v2*g)/(l2*l2)v1=l1*l1*l1

v2=l2*l2*l2

By the above 3 formulas. 1*l1=ρ2*l2

So. 1*ρ1*ρ1*l1*l1*l1*g*g*g=ρ2*ρ2*ρ2*l2*l2*l2*g*g*g（f1*f1*f1）/(f2*f2*f2)=(ρ2*ρ2)/(ρ1*ρ1)

1> 2

So. f2>f1

You can only choose D, in the case of the same pressure, the pressure is only related to the area, and the conditions in the question cannot judge the area at all, believe it, I scored 108 points in physics in the college entrance examination, and the full score was 120 (comprehensive).

Summary. The scientific problems in primary school are closely related to practical problems, and we must closely link book knowledge with practical life, so that we can understand the future, go deeper, use them, and create new things

We must closely link book knowledge with practical life, so that we can understand the future, go one step deeper, use it, and create new things

This one. First of all, which book must be read by the child? Who is the author?

You need to fill in these fields before you can read the following content.

For such a topic, the teacher will first give you a list of books.

Then go and read it.

For example, let's read an article on the use of a magnifying glass.

OK. Just copy what you think you have learned from the article into the air.

The content of the study can be ignited with a magnifying glass.

At noon, take a magnifying glass to adjust the direction, and put a piece of paper under the mirror, you can put some cotton wool on the paper.

Let the magnifying glass focus on the cotton wool, and you will find that slowly the cotton wool will turn black and smoke, and finally suddenly it will fall on.

I just need to fill in the two blanks as I said.

How many parts are you doing here?

The end result is that the magnifying glass has the effect of concentrating light.

Divide the above into several empty clocks.

Just divide the above into a few blanks.

1 Harvest: 2 Contents of the study: 3 Solutions: 4 Findings: You copy the line after the colon to each one no.

Dear, this job needs to be done by the child himself.

The first empty was voted in the article.

The rest is what was actually done.

You have to do this with your child.

Have your child write it down when you're done.

For a bucket with a dead weight of 10 N, the mass of the water in the bucket is 4 10- m The density of water = 8 kg The gravity of water is 8 10 = 80 N Then the total gravity of the bucket is 80 + 10 = 90 N (because the water is placed in the bucket).

From the above conditions, it can be obtained that the pressure of water on the bottom of the barrel p=water density*10N kg*

The pressure of the barrel on the table top is p=90n4 10- m (because the area of contact between the table and the barrel is the area of the bottom of the barrel) = 2250pa

The first void is calculated according to the PGH (p refers to the density).

Second, first find the volume of water, then the mass of water, and then the gravity of water, calculate the total weight of the bucket and water, and divide it by the area of the bottom of the bucket.

Pay attention to the conversion of units.

1) It cannot be used.

Hand. Touch the medicine, do not put.

Nose. Do not go to the mouth of the container to smell the smell of medicines (especially gases).

Taste. the taste of any medicine;

2), pay attention to saving drugs, should be in strict accordance with the dosage of the experiment to take drugs, if there is no indication of the dosage, generally should be taken according to the minimum amount, liquid take.

ml, solid only.

Cover the bottom of the tube.

3) The remaining drugs of the experiment can not.

Pour back into the original bottle. Don't be casual either.

Discard. Don't even take out the lab, put it in.

Designate. inside the container

4) Pay special attention to protecting your eyes during the experiment, in case the eyes are splashed with liquid medicine (especially corrosive or toxic liquid), immediately.

Rinse with water. Do not rub your eyes with your hands), blink your eyes when washing, ask a doctor if necessary, and advocate the use of protective glasses

5) There are the following common chemical instruments: test tubes, graduated cylinders, gas collection cylinders, which can be heated.

It cannot be used as a reaction vessel.

There is usually no scale.