High school physics puzzles, high school physics puzzles

Never do it in physics by looking at the answers while doing the questions, which will not hurt you in the short term, but your grades will definitely be bad in the long run, because the questions will not leave much impression on your mind. The most important thing in learning physics is to think, to think about the physical model, to understand every process, only this can have twice the result with half the effort.

For students like you, it is taboo to look at the answers while doing it, and it is best to look at it only after full thought. Doing questions is only one thing, the most important thing is to have a deep understanding of the knowledge points through it. I believe that your foundation will be fine after hard work, and you must not look at the master and the low.

It's good to look at the answer, but you have to think about it before you look at the answer.

Thinking and understanding play a big role in physics.

What you think is wrong. The essence of the induced electromotive force generation is the change in magnetic flux. Cutting magnetic field lines creates an induced electromotive force, also because of a change in magnetic flux. If the magnetic flux is constant, there is no induced electromotive force, which is the law.

The acceleration does not change when throwing up.

When falling**, only the time when it is in contact with the ground is that the acceleration is upward, and the magnitude is constantly changing.

When there is no contact with the ground, the acceleration is always g downwards.

The acceleration g is a vector quantity.

The direction is always straight down.

To be exact, it is always pointing to the center of the Earth.

The size is constant at 10 m s2

The first question: because the same amount of charge is the same, and the two balls are exactly the same, the capacitance is the same, so there is no change in charge after touching, and because there is no kinetic energy loss, so k=h

The second question: because of the same amount of heterogeneous charge, so the band point after the collision is 0, so the initial acceleration is g+a electricity, and the acceleration after the collision is g, so the initial force is greater than the force after the bounce, so in order to make the bounce up to the velocity is 0, so the distance should be k>h

Hand hit, give points.

It is indeed not simple for you to discuss this problem as a freshman in high school, let me tell you, the physical model of this problem is a uniformly charged sphere, characterized by the internal field strength of 0, and the external field strength of e= kq r 2, that is, from the outside, the electric field of the spherical surface and the electric field of the charge at the center point are equivalent, and the amount of electricity is the same, so your above algorithm is completely correct, the simplest way to do this problem is that the surface field strength of the object is equal to the charge surface density (the amount of electricity per unit area) (4 k), Just substitute the data directly.

There is no electric field inside the Earth, it's just"Equivalent"Nothing more.

Why is the distance getting farther away? The Q on the surface is distributed on the spherical surface, and the argument that you get farther away is just that you imagine that you concentrate all the Qs on the surface at one point, and it's the near point. If you put it on the other side of the ball, you will find that the distance is getting closer again.

r has a range, which can be interpreted as the range of r is: r > radius of the earth.

Pick C to catch up with the sun, so it's west. In the evening, the sun is in the west, so it is evening.

You have a good experience of this, it's not easy to describe.

cThe sun went down, and the planes flew after the sun. When the speed of the plane is high enough, the sun comes out.

A force analysis knows that the ball is subjected to downward gravity and elastic force in the direction of the rope.

The direction of velocity is along the tangent direction of the rope (perpendicular to the direction of elastic force).

So gravity works, elasticity does not work.

aA movement of a distance in the direction of the force is called work.

Gravity does positive work for a while and negative work for a while.

Choose D, because the elastic force and gravity are perpendicular to the direction of movement of the ball, and there is no displacement in the direction of the force, so no work is done.

aOnly gravity does work on the ball.

If the air resistance is not considered, only gravity and elastic force are subjected to the elastic force, and the elastic force is along the rope and perpendicular to the direction of movement, so no work is done, only gravity does work!

Analysis: This is a single pendulum-like motion, because the direction of the force given by the rope to the ball and the direction of the speed of the ball swing are always perpendicular during the movement, so the force on the rope, that is, the simple interest in the question, does not do work, and only gravity does work.

Regardless of air resistance, the process of motion is actually a process in which kinetic energy and potential energy are converted into each other under the action of gravity.

The easiest way to judge this kind of problem is to first assume that they are evenly balanced, and then judge the air pressure of each tube, and then judge whether the tube is rising or falling.

Mercury is discharged, assuming they descend to the same height. At this time, the proportion of the increase in the volume of the gas in the tube fiber is obviously c>b>a. That is, at this time, the pressure of pipe C is the smallest, the pressure of pipe B is second, and the pressure of pipe A is the largest.

The rest is good to judge, the A tube pressure is high, and naturally it will drop a little at the same hypothetical height, and the C tube will rise a little. The b-tube is clearly between the two of it.

Overcome gravity to do work, gravitational potential energy increases.

It's really about the understanding of overcoming. Of course, the premise is an understanding of basic physical concepts.

The original meaning of overcoming is to overcome with will and strength. Here is the work done by forces other than gravity to overcome the work done by gravity, that is, the direction of motion is opposite to the direction of gravity, gravity does negative work, and the gravitational potential of the object is too high, so the gravitational potential energy of the object increases.

Energy is conserved, and overcoming gravity is an increase in altitude, and this work becomes potential energy.