The second junior high school physics master helps, and the second junior high school physics asks f

v gold + v silver = 35 i.e.

m gold 1 + m silver 2 = 35

m gold 1 + (530-m gold) 2 = 35

The solution. m gold

It contains gold without considering the change in volume after mixing.

Contains 164g of gold

Rationale:1Let the gold content be m(kg), then the silver content is: (2.).Since the density of gold is 1, therefore, the volume of gold is:

v (gold) = mass density = m 1;

Similarly, since the density of silver is 2, therefore, the volume of silver is:

v (silver) = mass density = (

3.Because the total volume is 35 (cm3) = 35 * 10 (-6) (m3), so:

35 10 (-6) = v (gold) + v (silver) = m 1 + m 2, substituting the value of 1, 2 to get:

35^10^(-6)=m/(

4.Solving this equation about m yields: m=, so it contains 164g of gold

This kind of problem is just a list of equations.

Let there be gold v cubic centimeters in the alloy, then the equation according to the mass equality column is as follows:

1v+ρ2(35-v)=530

The volume of gold is solved, and then calculated using the mass formula m= v.

Let the gold volume v1Silver v2v1 + v2 = at this time the unit is converted into grams per cubic centimeter, gold m = ?

The amount of series connection is very simple, as long as the electrical appliances, power supply, and switch are connected end to end, and the parallel connection is to form two circuits, but the power supply and a switch are common on it, will you draw a physical picture, straighten it up, simple can be said, now the second year of junior high school will not be rare.

You still ask your teachers more, or read more reference books, ask your parents, etc., and hope that you will get a good score in the final exam, (

Oh combined with the physical picture.

It is the power supply (note to draw one long and one short).

A is the ammeter (A is drawn inside a circle).

x is the light bulb (x should be drawn in a circle).

o is the switch (the picture should be drawn well, the computer can't play it).

If the circuit diagram is rectangular and right-angled, you should add points when connecting parallel circuits, oh, you don't usually listen to the lecture carefully, we finished the exam in Haizhu today.

Circuit diagram: horizontal and vertical, don't draw corners of the components, connect in series along the current one by one, connect in parallel along the current one by one, and find the shunt point and confluence point one by one.

Physical diagram: The series is connected one by one along the current, and the parallel connection is connected one by one along the current, and the key is to find the shunt point and the confluence point, and pay attention to the wire does not cross.

Draw the objects of the real picture into electrical symbols according to their positions, and then take them according to the real picture and connect them with wires.

。。。I learned circuits in the second year of junior high school, which is amazing. But can you be specific? The main thing is to pay attention to the direction of the current, the positive and negative poles, and the ammeter and the voltmeter, the ammeter is not connected in series, the voltmeter is not connected in parallel, and the sliding rheostat should be noted.

1. Because electrons have a negative charge and the nucleus has a positive charge, an object with a negative charge has excess electrons. Because the rubber rod has a negative charge after rubbing against the fur, the rubber rod carries excess electrons (electrons are easy to get), so the fur is prone to losing electrons.

2. The rubbed rubber rod has a negative charge, and the negatively charged object can attract the small object that is not charged or positively charged. So the ball is positively charged or uncharged.

The essence of triboelectric power is the transfer of electrons. Since the rubber rod has a negative charge, it means that the electrons of the fur are transferred to the rubber rod, and it is natural that the fur is more likely to lose electrons.

Question 2: Uncharged.

(1) If the ball is repulsed, then the ball is negatively charged;

2) If the ball is attracted, then the ball is positively charged or uncharged

1 In the circuit of a metal wire, the orientation of free electrons forms the current, the voltage is the cause of the current, and the resistance is the conductor's obstruction of the current.

2 Only the washing machine and the electric oven are working in the home circuit, and the current through them is measured respectively. And the main circuit current of the circuit is 220 V at both ends of the washing machine and 220 V at both ends of the electric oven.

Because the internal resistance of the battery increases, the output voltage decreases.

4.There is no answer.

1. Directional movement of potential difference resistance.

2. 220 220 (Isn't this question a bit .......)3. A (The button battery of the electronic meter is 3V voltage; After the dry battery is used for a period of time, it is not the voltage that changes, but the internal resistance).

4. Isn't this question correct? There is no wrong ......

These questions seem to be junior high school content, right? ......It was a long time ago, and I forgot about ......

1: Move the voltage resistor in a directional direction.

3:d (the output voltage drops due to the increase of internal resistance after the dry battery is used).

4:d (if there is current in the circuit, the voltage cannot be equal everywhere).

The first question, directional movement, directional movement of free electrons, electrical resistance. Question 2, Question 3, DFourth, the answers are obviously all correct, if you don't make a mistake, there are no options in this question that match the meaning of the question. Hope it helps.

1. Red The focal length of red light to the convex lens is large, because the wavelength of red light is longer than that of violet light, and the degree of refraction is smaller than that of violet light. 2、d

1.Red; The convex lens has a large angle of refraction of red light.

This summer, I spent a lot of time reading the book "Interesting Physics" carefully. Very good, for me who was new to physics and chemistry at that time, this book is very magical, and a series of interesting chemistry, similar, are good, can be given to students who are curious and not satisfied with textbook knowledge, I didn't know much about physics before, and I was not very interested in this subject, but after reading this book, I really understood physics, and I had a strong interest in physics, physics is really an interesting subject. It allows us to learn about every aspect of life, and some peculiar phenomena.

From this work, many difficult, interesting, complex or unexpected physical phenomena related to physics are collected from daily life, science and technology, nature and science fiction, and the content involves all aspects of physics, including the basic laws of mechanics, heat, electromagnetism, optics, acoustics and various phenomena.

This book made me love physics even more and love life.

I think you should look for a language master...

Do you think that good physical expression skills are necessarily excellent?

Everything that should be said upstairs has been said.

Summarize the knowledge of this book, write as much as possible, and use physics knowledge, it should be possible.

wc！Classmate, you went wrong and classified.

I'm a master, but I haven't seen it, sorry

This has nothing to do with whether you are a master or not.

Let the width of the river be s and the height of the building be h

Then there is s (h - 10) = cot30 and s (h + 10) = cot60

Comparing the two equations yields (h-10) (h+10) = 1 3 to obtain h = 20

by =m v

Get v=m =......=

v=sl s=4mm 2=4x10 -6 m 2, so l=v s=......=2500m

Because 2500m 2000m

So that's enough!

Thick and thin converge and thin and diverge.

At two times the focal length and one time the focal length becomes smaller, smaller.

Anterior concave lens and posterior convex lens.

Magnifying the projector zooming out the camera magnifying the positive and virtual magnifiers.

Second, multiple-choice questions. Choose C