The speed of rotor of three-phase asynchronous motor is the speed of rotating magnetic field () the electric power input by DC motor is the rated power of motor () When the electromagnetic torque of the motor is greater than the load torque, the system is in deceleration state (). In order to obtain the highest efficiency, the DC motor must run with rated load () You'll get it right or wrong

The speed of rotor of three-phase asynchronous motor is the speed of rotating magnetic field () the electric power input by DC motor is the rated power of motor () When the electromagnetic torque of the motor is greater than the load torque, the system is in deceleration state (). In order to obtain the highest efficiency, the DC motor must run with rated load () You'll get it right or wrong

The speed of three-phase asynchronous motor rotor is the speed of rotating magnetic field (×)
The input power of DC motor is the rated power of motor (×)
When the electromagnetic torque of the motor is greater than the load torque, the system is in deceleration state (×)
In order to obtain the highest efficiency, DC motor must operate with rated load (√)

With a 20 meter long rope around a tree trunk for six circles, there are still 1.16 meters left. How many meters is the diameter of the tree trunk?

1m = (20-1.16) / 6, 3.14

In the international system of units, the main unit of length is (), and the common units are () ()
Should we fill in meter, kilometer, decimeter, centimeter, millimeter, micron and nanometer in turn

Yes, they should be meter, kilometer, decimeter, centimeter, millimeter, micron and nanometer in turn

When two pieces of wood are stacked together, M1 = 1kg, M2 = 2kg, 1 on the ground, the maximum friction between them is 2n, and the ground is smooth
Please give a specific explanation, thank you!
Under the action of the pull force F acting on M1, what is the maximum pull force when two pieces of wood do uniform acceleration motion together

How about a complete title
Stress analysis of M1 and M2 respectively (the analysis on the horizontal plane is enough)
M1 is pulled by F, and M2's friction against it - F,
M2 is only affected by the friction F of M1 against it,
Using the formula F = ma
F-f=m1a
f=m2a
The maximum f is 2n
So f Max is 3N
I haven't studied physics for many years, right

How many square meters is one mu?

Mu is China's municipal land area unit, one mu is equal to 60 square feet, about 666.67 square meters. Fifteen Mu is equal to one hectare

A piece of metal is weighed as G in air and 5g / 6 in water. Calculate the density of the piece of metal

G = F + F spring scale = P water V + F spring scale = P water V / P metal + F spring scale
It is found that P metal = 6p water V / g

It is known that the length of a right triangle is 195.2, and the corresponding angle is 40

If the slant length is a, then sin40 ° is 195.2/a. The value of sin40 ° can be obtained by looking up the table and substituting it, so the slant length can be obtained
The formula of the side length of a right triangle is unheard of. For example, if you know the angle and the right side, you can find it according to the definition of sine and cosine or tangent and cotangent

On the topic of Newton's law, two objects a and B with mass M1 M2 are superposed on a smooth horizontal plane
Two objects a and B with mass of M1 M2 are stacked on a smooth horizontal plane. Now, by pulling B horizontally, the acceleration of the two objects moving uniformly is a. if we use horizontal force to pull a, we still need to make the two objects moving uniformly with acceleration a ', then what is the maximum value of horizontal force?

The maximum static friction between AB is equal to the sliding friction, set FM
In this paper, we use the horizontal lira B to make the two objects do uniform acceleration motion together. The acceleration is a
For a: FM = m1a
If we use horizontal force to pull a and set it as f ', we still need to make the two objects move uniformly with acceleration a'. The maximum static friction between ab can only be FM
For B: FM = M2A '
a'=fm/m2=m1a/m2
For a: F '- FM = m1a'
F'=fm+m1a'=m1a+m1*m1a/m2=m1(m1+m2)a/m2

Since a negative number multiplied by a negative number equals a positive number, what number does a negative number multiplied by a positive number equal?

Negative numbers, just remember that two identical multiplications are all positive numbers, and two different multiplications are all negative numbers

A car braked at an acceleration of 2m / S2 to make a uniform deceleration linear motion, and the displacement it passed in the last 1s before it stopped moving is______ ．

If the motion of a car is regarded as a uniform acceleration motion with zero initial velocity in the opposite direction, the displacement of the car passing through in the last 1s after braking is reverse, and the displacement in the first second of uniform acceleration motion with zero initial velocity is x = 12at2 = 12 × 2 × 12m = 1m, so the answer is: 1m