A few physics questions, no points, but sincerely ask

Let me tell you.

1. The electric field strength is called the change gradient of electric potential, which is the derivative of the electric potential to space, the electric potential is the integral of the electric field to the space, the electric potential is unchanged, the electric field must be 0, do not use e= u d, this is just a special case.

2. Period, frequency, angular frequency w are all physical quantities that describe the periodicity of motion, the three are derived from each other, they depend on the system itself, and have nothing to do with the initial conditions, such as a single pendulum, regardless of gravitational acceleration, as long as the pendulum length is constant, all three are constant, 3. The change of the total momentum of the particle system has nothing to do with the internal force.

The change of the total kinetic energy of the particle system is related to the conservative internal force, and the change of the total mechanical energy of the particle system is not related to the conservative internal force, such as the ** class, which is the conversion of the work done by the conservative internal force into kinetic energy.

The condition for the conservation of mechanical energy is that only conservative internal forces do work, and of course it has nothing to do with conservative internal forces.

, U--potential difference, D--distance, electric potential U does not change, so the potential difference is 0, that is, E is zero.

2.The period of harmonic vibration is only related to the period of the source, what is the period of the source The movement period of harmonic vibration is how much, the closer the natural frequency and the frequency of the source, the greater the amplitude, and the natural frequency is only related to its own material and size, and has nothing to do with w.

3.First of all, we rarely study the particle system, generally speaking, the particle system involves the total amount, the total mechanical energy is conserved, the total momentum is conserved, and there is little research on the relationship between the particle system and the conservative force, and the relationship between the single particle is generally said to be the relationship with the conservative force.

1）.The conservation of momentum is applicable under all conditions, and the total momentum within the system is never the same and has nothing to do with the internal forces.

2）.Containing potential energy, the change of total kinetic energy of the particle system is related to the mutual potential energy generated by the internal forces between the particles, that is, the kinetic energy is converted into potential energy.

3）.If there is no loss in the propagation of the wave, the change of the mechanical energy of the particle system is not related to the conserved internal forces, because the mechanical energy of the system is conserved.

AM is amplitude modulated broadcasting, the frequency is generally 3 30MHz, it belongs to the medium wave, curve propagation, is an electromagnetic wave.

When doing the calculation problem, the propagation speed of electromagnetic waves in the air is equal to the speed of light c 3*10 8m s according to the wavelength formula v=f*, because f 954000hz, v c 3*10 8m s

So the wavelength v f

am stands for Amplitude Modulation. When you do the question, you can directly think that the radio wave is emitted at a frequency of 954kHz, and you can ignore AM

Amplitude modulation broadcasting, the frequency is generally 3 30MHz, belongs to the medium wave, curve propagation, is an electromagnetic wave.

am stands for Amplitude Modulation.

fm stands for Frequency Modulation.

This problem can be solved with relative motion. When the A ball falls 1m, its velocity is under the root number (2g), which is replaced by VA. At the same time, the B-ball also started to fall with a velocity of 0.

Since both balls are in free fall and the acceleration is the same, ball A moves in a straight line with uniform velocity relative to ball B, and the relative velocity is va. When A and B reach the ground at the same time, A moves 7-1=6 meters relative to B, and the time for A and B to move together is 6 VA, so the final velocity of ball A is VA+6*G VA=4*under the root number (2G). The height of the tower can be found to be 32g2g2 2g=16g=

Solution: The motion of the iron chain is the free fall motion, we analyze the motion of the point on the iron chain, that is, the motion of point a, the time of falling m at point A and the time of falling ( m is the difference is s, and we find L. with this relation

Let the length of the chain be l, then the time for a to fall m is t1, and the time for falling ( m is time t2, so the formula h=1 2gt 2 is obtained:

t1-t2= ③

From the equation l= m

aSince the presence of q0 will redistribute the charge on the large conductor, and the surface charge density near q0 increases (because it is a different charge), so f q0 is stronger than the original field.