I don t need to solve the problem, just help me analyze the answer

After the ball leaves the inclined plane, it makes a flat throwing motion.

If the fall height h is measured, the fall time t= (2h g) can be obtained.

Then measure the horizontal displacement s, and the horizontal initial velocity is obtained

v=s/t=s/[√(2h/g)]

In the process of sliding, the support force does not do work, only gravity and friction do the work. According to the kinetic energy theorem:

mgh+(-w)=(1/2)mv²

Solution, w = mgh-(1 2)mv = mgh-(1 2)m = mgh-mgs (4h).

This is the work done by the ball to overcome the resistance, which is greater than zero).

The work done by friction on the small ball: -[mgs (4h)-mgh].

I'll give you my thoughts first. I think it's easy to use the kinetic energy theorem. On the surface, set the highest point as point A and the tangent point as point B. After doing a good acceptance analysis, it can be known that object B only collects gravity and friction to do work from A to B.

Then w weight (known) - w friction (target sought) = h (surface height, to be measured) g (object gravity, known) - (2 h) f

Then use the flat tossing theorem to find the work done to b, and f can be obtained

I've only finished reading it in my first year of high school.,Please point out the mistakes.,As for the equipment of the first question and the second question to be measured, there should be no need to explain.。。。

First, find the velocity of the wooden block B sliding to the table, which can be found using the experimental knowledge of flat throwing motion, and then according to the amount of mechanical energy lost is equal to the work done in friction.

Analysis: In 1992, Comrade ***'s southern speech lifted the foundation and caused people to be confused about the issues of "simple chain planned economy is socialism" and "market economy is capitalism", and the development of market economy became a consensus, so there was a "tide in the sea" in society. So the answer is a.

Answer: a

There are so many questions!

It's completely an radical operation, and according to the textbook, it can definitely be done.

For example, question 11:

The root number 12 can be written as the root number 3 multiplied by the root number 4, and this root number 4 is 2

Multiply the root number 3 by the root number 3 at the end of the head, which is 3

Another example is question 12:

8 times 25 is 200

200 = 2 times 100

100 square is 10

2 can't be opened, and can only be kept as the root number 2

Negative multiplied by negative, is a positive number. You know that).

Don't know, don't know, don't know, don't know, don

（ ）=9

Let x-y=9, z-w=14, x +z=12, y +w=2, then x-y=9(1).

x+z=12（2）

z-w=14（3）

y+w=2（4）

4）+（3）:z-w+y+w=2+14

y+z=16(5)

2)-(1): x+z-x+y=12-9y+z=3(6)

5) (6) Contradictions.

Therefore: there is no solution to the original system of equations.

That is: there is no solution to this problem.

1) Real numbers.

m square + m - 2 = 0

m+2)(m-1)=0

m=-2 m=1

2) Imaginary numbers.

m square + m - 2 = 0

m+2)(m-1)≠0

m≠-2 m≠1

3) Pure imaginary numbers.

m square + 3m + 2 = 0

m square + m - 2 = 0

m=-1

Answer: (4) After the reaction of carbon dioxide and sodium hydroxide, the chemical equation is CO2 + 2NaOH = Na2CO3 + H2O

After the addition of dilute hydrochloric acid, the chemical equation is Na2CO3 + HCl = NaCl + H2O + CO2 (gas mark).

Hence the creation of bubbles.

After the addition of lime water, the chemical equation is Na2CO3 + Ca(OH)2 = CaCO3 (precipitation symbol) + 2NaOH

As a result, a white precipitate is produced.

5) There is a white precipitate in the first bottle, and it is concave inward; There is no precipitation in the B bottle.

Ca(OH)2+CO2=CaCO3 +H2O bottles bulge again, because Na2CO3+HCl=NaCl+H2O+CO2 requires memorization of chemical equations, otherwise it will not be possible.

<> the state of the vertical sensitive sail branch rush.

The last question, it should be +y, right?

The shortest distance of OP is good from the OP AB, and it can be seen that the OPA of the front sock is a straight and hidden lead triangle OA=10cm AP=8cm

then op*op= oa* oa-ap*ap=36

op=6cm