The others are 25%, the medical books are 35%, and the agricultural books are 40% (1) How many books are there in this library (2) How many agricultural books are there (3) How many medical books are there

The others are 25%, the medical books are 35%, and the agricultural books are 40% (1) How many books are there in this library (2) How many agricultural books are there (3) How many medical books are there

(1) How many books does the library have in total = 9600 / (40% - 35%) = 19200 (volumes);
(2) The number of agricultural books = 192000 * 40% = 76800 (volumes);
(3) The number of medical books = 192000 * 35% = 67200

It is known that there are 16000 medical books, 9600 more agricultural books than medical books. What is the percentage of agricultural books? What is the percentage of other books?
Medical books: 25% other books: {}% agricultural books: {}%

Agriculture: 40% others: 35%

What is "voltage on a circuit"?
How to connect the voltmeter?
How to read on the voltmeter?

In order to generate current in a section of circuit, there must be voltage at both ends. The function of power supply is to provide voltage for electrical appliances, so the voltage on the circuit refers to the power supply voltage. 2. The voltmeter should be connected in parallel with the measured electrical appliances, and the positive terminal of the voltmeter is connected to the positive terminal of the power supply, and the negative terminal of the voltmeter is connected to the negative terminal of the power supply

When an object moves in a straight line with uniform acceleration, the displacement in the first second is 6 m, and the average velocity in the second is 9 m / S. (1) calculate the acceleration of the object; (2) calculate the displacement in the third second

(1) The displacement in the second second second is x2 =. VT = 9 × 1m = 9m. According to the displacement difference in continuous equal time is a constant, we get x2-x1 = at2, so there are: a = x2 − x1t2 = 9 − 612 = 3m / S2; (2) according to x2-x1 = x3-x2 = at2, the displacement in the third second is X3 = 2x2-x1 = 2 × 9-6 = 12m. (1) the acceleration of the object is 3m / S2; (2) the displacement in the third second is 12m

Optics, mechanics, all formula concepts

[mechanics] 1. Velocity: v = s / T 2, gravity: g = mg 3, density: ρ = m / V 4, pressure: P = f / S 5, liquid pressure: P = ρ GH 6, buoyancy: (1), f floating = f '- f (pressure difference) (2), f floating = G-F (apparent gravity) (3), f floating = g (floating, suspension) (4), Archimedes

The mass of the frame is m, the mass of the spring is neglected, and the stiffness coefficient is K. a small ball with mass m is hung under it. Let the ball vibrate up and down in the vertical direction
In the vibration, the frame does not leave the table, but when the ball rises to the highest position and the speed is just zero, although the frame does not leave the table, there is no interaction pressure and supporting force between the frame and the table. The acceleration of the ball at this moment is?
(quick solution)

At this time, the frame gives the ball a downward force through the spring, and the ball gives the frame a force of the same size, so that the pressure of the frame on the desktop is zero
Then, the force is equal to the gravity of the frame
F=Mg
This force also acts on the ball to produce an acceleration of 0
a'=Mg/m
At the same time, the ball has a gravitational acceleration
a=a'+g=（M+m)g/m

The current of LCD electronic calculator is about 130___ The silver oxide batteries for electronic watches have a voltage of___ 5. The current of transistor radio is about 10 ~ 100___ .

UA, 1.25 ma

Weight loss of spring dynamometer
Why can we use a spring Dynamometer on the surface of the earth instead of weightlessness?

A spring dynamometer measures force, not gravity

Given that the area of a square is 11cm square, find its side length

Its side length = √ 11cm

The length of a light spring is 20 cm, the upper end is fixed, the lower part is hung with 20 N object, and the static spring becomes 30 cm?
2. If two people hold the two sides of the spring respectively and pull with 15N force at the same time, how long will the spring become?
3. If half of the spring is cut off, what is the obstinacy coefficient of the remaining half?

1. When the object is stationary, the spring tension is equal to the gravity of the object. From mg = k * x, 20 = k * (30-20), k = 2 N / cm2. If two people hold the two sides of the spring respectively and pull with 15 N force at the same time, the spring tension is 15 n. from F = k * x1, 15 = 2 * x1, X1 = 7.5 cm