What are the knowledge points of high school physics dot timer?

Belch. Classmate, I solemnly tell you that the answer is wrong.

We've done n more than one of these problems, and every four points the selected counting points are, and those two should be right!

All right. We are now in our third year of high school, and we have done this type no less than dozens of times.

Our common question type is to select a counting point every four points. So our cycle is 5*. So a simple analogy to this topic, it is easy to find that it should be 3*!

This kind of question can actually be asked directly to the teacher, if there is a little bit of controversy, it is more interesting to discuss with the teacher, you say that there are two kinds of answers to the online questions, and the teacher will be very patient to answer for you.

Good luck.

Of course it's 2.,You misunderstood.。。。 The first and third of these three points are counted as time, not twice at four points.

Every two points is a count of seconds every three points.

I saw your question in the afternoon, and no one answered it?

Constant velocity, the interval between the points is uniform, if you look at the diagram, C agrees, A feels that the distance is a little inconsistent, because it is not obvious.

Go faster and faster: the dot interval is getting larger and larger, and b is in agreement.

Paper tape d is fast first and then slow.

50Hz power frequency, then the interval time of each point is seconds, and each value can be inferred according to S=VT.

There are only numerical values on the graph, and there are no units, so it cannot be calculated.

The knowledge points of high school physics dot timer are as follows:

1. When using the timer to dot, the power should be turned on first, and then the Xun's paper tape should be released after the dotting timer is stable.

2. The dotting timer should be marked on the paper tape with a small dot of appropriate weight, if it is a short horizontal line, it should be adjusted to increase the height of the carbon paper from the carbon needle.

3. Electromagnetic dot timer.

It is a timing instrument that uses AC power.

4. Dotting timer difference method.

The difference-by-difference method is to improve the utilization rate of experimental data and reduce the random error.

It can also reduce the instrument error component in the experiment, so it is a commonly used data processing method.

5. Electromagnetic dot timer is a kind of timing instrument that uses AC power supply, its working voltage is less than 6V, generally 4 6V, the frequency of the power supply is 50Hz, and it is powered every other day.

Understand the construction of a dot timer; Will use a dot timer to study the law of the speed of an object with time; By analyzing the paper tapeAssayUniform variable speed linear motionacceleration and its velocity at a certain moment; Learn to use image method and list method to process experimental data.

First, the purpose of the experiment.

1. Practice using the dot timer and learn to study the movement of objects with dotted paper tape.

2. Measure the acceleration of linear motion at uniform variable speed.

Second, the principle of experiment.

1. Electromagnetic dot timer.

Operating voltage: 4-6V AC power supply.

Dotting period: t=, f=50 Hz.

2. EDM timer.

Operating voltage: 220V AC power supply.

Dotting period: t=, f=50 Hz.

Dotting principle: it uses spark discharge to punch a small hole in the paper tape and display the timer of the dots, when the 220V AC power supply is turned on, when the pulse output switch is held according to the cavity, the pulse current of the timer is connected to the discharge needle of the positive pole.

The toner paper disc to the paper disc shaft connected to the negative electrode produces an electric spark, so Wu slips on the paper tape and lays a series of dot traces.

3. Experimental equipment.

Trolley, string, hook yard, fixed pulley attached to one end.

The long wooden board, EDM dot timer (or dot timer), low-voltage AC power supply, two wires, paper tape, meter ruler.

About the dot timer, you should know: the dot timer is mainly divided into two categories, namely electromagnetic dot timer and electric spark slag dot timer; The working voltage of each type of dot timer, its advantages and disadvantages, you need to master. When using the dot timer to do experiments, you also need to understand what the experimental principle is; Finally, you need to learn how to process the paper tape that is punched out by the dot timer and calculate the speed and acceleration of the object's motion.

1.The object is moving at a constant acceleration, the bridge lets the distance traveled in the same period of limb time.

2.Friction factor and kinetic friction.

3.Newton's second law holds the world (f=ma).

A dot timer is a tool for measuring time. If the paper tape driven by the moving object passes through the dot timer, the dots on the paper tape record the time of the object's movement, and the dots on the paper tape also indicate the position of the moving object at different moments. By studying the spacing between the points on the paper tape, the frequency of motion of the object can be analyzed.

Electromagnetic dot timer is a kind of timing instrument that uses AC power supply, its working voltage is less than 6V, generally 4 6V, the frequency of the power supply is 50Hz, it beats every other time. That is, 50 points per second. The EDM timer is a timing instrument that uses spark discharge to hit the ink on the paper tape and shows the dot trace, using 220V AC voltage, when the frequency is 50Hz, it hits the dot every other time, when the EDM timer works, the resistance to the movement of the paper tape is relatively small, and it is smaller than the experimental error of the electromagnetic dot timer.

EDM principle: The electrode geometry is cauterized on a metal (conductive) component using a discharge electrode (EDM electrode) with a specific geometry. The electrodes of the EDM timer are dot-shaped.

Electric spark is a kind of self-excited discharge, which has the following characteristics: The two electrodes of spark discharge have a high voltage before discharge, and when the two electrodes are close, the medium is broken down during the period, and then spark discharge occurs. As the breakdown process occurs, the resistance between the two electrodes decreases dramatically, and the voltage between the electrodes decreases dramatically.

The spark channel must be extinguished in time after maintaining a short period of time (usually 10 -7 10 -3s) in order to maintain the "cold pole" characteristic of the spark discharge (that is, the heat energy converted by the channel energy does not have time to reach the depth of the electrode), so that the channel energy acts on a very small range. The effect of channel energy can cause local corrosion of the electrode.

The principle of the dot timer, did you understand it back then?

Dot up timer.

The dotting time interval is equal to the reciprocal of the power supply frequency.

Therefore, when the power supply frequency is lower than 50Hz, the dot cycle is greater than , at this time, if it is still calculated according to 50Hz (that is, the dot interval is still calculated by S), it can be seen from v = x t: the displacement is the same as x, and the time is calculated, then the time t is smaller and the leakage is smaller, so the speed v is larger than the real value.

s=vt+1/2at2

Take the first segment s=, t=, known a=5m s2

Substitution is obtained v=