"On a horizontal ice surface with a horizontal thrust of size F = 20 N, an ice cart with a mass of m = 60 kg is pushed from a standstill. The friction force experienced by the ice car is 0.01 times the pressure on the ice surface, and when the ice car advances 30m and then removes the thrust F, the ice car advances for a distance and then stops. What is the velocity and total distance of the ice car when the thrust F is removed? ”

The physics teacher pushed his glasses, and after seeing that no one was speaking, he could only put his eyes on the penultimate row by the window:

"Yang Chao, you answer!"

"According to the kinetic energy theorem, the amount of change in the kinetic energy of an object is equal to the work done by the resultant external force. According to the problem, the mass of the object is known and does not change, so the equation can be solved by calculating the initial and final state velocities. ”

"That's correct, but why not use Newton's second law, which is easier to understand?"

The physics teacher looked at Yang Chao with a smile, and he was not surprised at all that this student was able to answer this question.

"The whole object is divided into two states in the process of change, and the use of Newton's second law requires the analysis of the force in the presence of thrust F and the absence of thrust F, but the use of the kinetic energy theorem only needs to consider the initial and final states, and does not need to consider the intermediate process."

"Correct answer, please be seated!"

As soon as Yang Chao sat down, a whispering voice sounded near him.

"That's amazing!"

"Yes, Yang Chao is really amazing!"

"How could I not have thought of it?"

Hearing the admiration around him, Yang Chao smiled faintly, this kind of question, but any student from China, as long as he has studied physics a little seriously, there is no difficulty in answering. After all. China's basic education is far ahead of the rest of the world.

He looked out the window, it was the school's archery department was practicing outdoors on the playground, Yang Chao swept his gaze, and found that familiar figure.

"Jingle bell!"

When the bell rang for the end of class, Yang Chao was immediately surrounded by a group of people.

"Classmate Yang Chao, can you please teach me how to do this question?"

"Yang Chao. Let's go to the library this weekend to revise, shall we? ”

"Classmate Yang Chao, why don't you come to my house tonight?"

Just when Yang Chao was dizzy and uneasy by the noise of this group of people, someone appeared and saved him in time: "Yang Chao, you come to my office!" ”

Seeing that it was the teacher who spoke, the classmates stopped blocking him and let him leave.

As soon as he entered the office, the teacher who brought Yang Chao to the office said with a serious expression: "Yang Chao, I think there are some things we have to communicate." ”

"Say it. What's the matter? ”

Seeing Yang Chao's calm expression, the other party was anxious:

"Why are you still so calm? It's been three days since we've been here for three days, but so far it's just the four of us here, and the others haven't heard anything at all! And we never received a reminder from the system about the main quest, and even, even the plot didn't unfold, don't you think it's strange? ”

"Calm down, Kong Zhang."

Yang Chao glanced at this reincarnation that he had known for a long time. Said slowly.

"How do you tell me to calm down? It's just that the main plot line hasn't unfolded, but until now. We're half as many! The most important thing is that we have lost contact with Gong Weiyang! Don't forget why we came to this copy. ”

Looking at Kong Zhang's excited appearance, Yang Chao frowned slightly, after returning from the last copy, due to too many things, his mentality has undergone a fundamental change, so he is slightly disgusted by Kong Zhang's current performance.

Disgust is disgust. However, after all, the other party is his ally, Yang Chao still said patiently: "Even if you are in a hurry now, it will be useless, this copy Gong Weiyang wants, if he finds out that he has lost contact with us, he will naturally find a way to come to us." As for the task you mentioned. I think the system will be released when those zombies start appearing. ”

"Of course I do! Are we just doing nothing now? I think you seem to enjoy being a top student! ”

"Tell me, then, what can we do now? Or do you think we can't deal with those zombies? ”

Kong Zhang was speechless.

"Enjoy the temporary peace in front of you, maybe tomorrow the zombies will start to invade."

After leaving such a sentence, Yang Chao turned around and left the office.

In fact, Kong Zhang was right about one thing, that is, Yang Chao did enjoy such a quiet life, especially after experiencing the last quest dungeon.

There is still one class before school time, and Yang Chao has to go to the gun path department after school, because in this copy, he is from the gun path department of the vine beauty garden-

"The Lord! Is today's event still going on as usual? ”

A young girl full of youth suddenly ran over from the other side of the corridor, stopped in front of Yang Chao and asked.

"Well, it's business as usual!"

"Yay! That's great! Does the Lord know that? Among the third-year students, you are one of the few who are still participating in the activities, and most of the third-year leaders of the activity department have stopped the activities due to study reasons! ”

"Really?"

Yang Chao nodded, noncommittal, he wouldn't care about these things.

"By the way, the chief general of the kendo club said that she is coming to challenge you today."

"Kendo club?" Yang Chao said to himself.

Evening.

The activity room of the gun path department of the Fuji Art Garden.

"Hirai, sit down a little lower, and shift your center of gravity down."

"Ono, the speed should be fast, the position should be accurate, the shot should be powerful, remember three words, fast, accurate, ruthless!"

"Miyamoto, where are your eyes looking? If this was on the battlefield, you would have been killed by the enemy long ago! ”

Yang Chao looked at the members of the Gun Dao Department who were training, and methodically corrected their mistakes.

At the same time, the crowd who was watching the training of the gun path department was also talking secretly.

"Yang Chao's predecessors are still as strict as ever!"

"Of course, since a few of their Chinese exchange students came to our school last year, Senior Yang Chao has picked the entire gun path department by himself! Do you know? The original main general, Hikawa Gangsaka, was defeated without even catching a move from Yang Chao's predecessor! ”

"What, there's such a thing?"

"What do you think? Otherwise, how could the people of the Gun Road Department be convinced to let a Chinese exchange become the main general? ”

"This is probably the legendary Chinese kung fu, right?"

"I think that's it."

At this moment, a rather mature female voice came from the door of the activity room:

"The head of the kendo department, Poison Island Tsuinzi, and the deputy chief general, Cheng Ying, came to visit the gun department." (To be continued.) )