There is a trap in this question in Chapter 3!
Xu You was ready to face the test.
Although it was just a small test, it was the first battle that Xu You fought after experiencing the deep learning state.
Xu You really wanted to see what kind of results he had achieved after studying for a lesson.
After taking the test paper, Xu You first took a quick look at it.
Sure enough, the question types were basically the same as those in the monthly exam just now.
Even some easy-to-make mistakes in the monthly exam have been carefully integrated into this quiz.
Xu You maintained a deep learning state and started answering questions at full speed.
At this time, the bell rang.
Some students stood up and went to the bathroom.
Some students did not care about what the physics teacher said and ran to the playground to relax.
Although there were students moving around, the classroom remained relatively quiet overall.
After all, it is an exam, so we still have to show some basic respect.
Except for a few students who were writing furiously.
Most of the students are still confused by the questions in the quiz.
Everyone is looking through previous monthly exam papers, looking for similarities.
Or check with your deskmate to see if he or she has solved the problem.
But more often than not, the classmates just looked at each other in bewilderment.
"This problem can be solved directly by comparing the law of uniformly accelerated linear motion."
"For dynamic analysis of the equilibrium of concurrent forces, just draw a vector triangle."
"This is not exactly the same question type as the monthly exam, it's just a change of numbers."
Under the state of deep learning, Xu You's answering results were surprisingly good.
The previous questions encountered almost no resistance.
At most, they were just questions that required calculations, and I spent a little time on the calculations.
What Xu You didn't notice was.
His exaggerated state had been seen by his deskmate Dong Chao.
"Xu You... is this a demonic barrier?"
From Dong Chao's perspective, Xu You seemed to be driving at double speed.
Without even looking at the question, he quickly wrote down the answer.
Completely different from the Xu You that Dong Chao had in mind.
Dong Chao's usual grades are slightly worse than Xu You's.
But his speed in solving problems is faster than Xu You's.
Xu You is a famous student in the class . He studies very hard, but his academic performance is not that outstanding.
In terms of answering speed, it is also on the slow side.
Dong Chao even suspected that Xu You was writing the answers randomly.
But when Dong Chao saw the clear process on Xu You's paper.
I also feel like this isn't something that was written casually.
Just over ten minutes had passed.
Xu You finished the last big question.
This big question is obviously more difficult than the previous ones.
Although the question types are similar to those in the monthly exams, there are some changes in them.
This is also the reason why the physics teacher set the passing score for this quiz at 80 points.
It is understandable that I lost points on this last big question.
But for other questions, there is really no reason to lose points.
This is a conveyor belt problem and also a difficult point in the mechanics section.
This type of question tests students' independent analytical ability.
Even if you have mastered the answering skills, you still need to accurately analyze and understand the questions in order to get full marks.
"First, compare the coefficient of kinetic friction and the tangent of the inclined plane to determine the relationship between the sliding friction force and the downward component of gravity along the inclined plane, thereby determining the direction of the object's acceleration."
Xu You did not feel at a loss because of the change in the difficulty of the questions.
Instead, I immediately clarified my thoughts and determined the starting point of the question.
This is also an idea mentioned by the physics teacher in the last class.
In the deep learning state just now, Xu You has fully understood this idea and kept it in mind.
Soon, Xu You determined the direction of the object's acceleration and calculated the magnitude of the object's acceleration based on Newton's second law.
The overall topic began to become clear.
“That’s the feeling!”
Although it was just a beginning, Xu You had already found an excellent feeling for solving the problem.
The acceleration value obtained through mechanical knowledge is then incorporated into the kinematic formula.
Xu You quickly solved the first question: the length of the scratch on the conveyor belt.
This first question is not difficult to answer.
But if they can solve it skillfully, it at least shows that the students have a good grasp of the basics of motion and force.
You know, just the big questions about motion and force are enough to stump more than half of the students.
Xu You did not feel proud, but immediately devoted himself to the second question.
Find the speed of the small object when it leaves the conveyor belt.
Simply put, this problem is about the movement of an object that first decelerates downward along a conveyor belt and then accelerates in the opposite direction.
As long as the displacement and acceleration are determined, the formula can be used to calculate the speed of the small object when it leaves the conveyor belt.
Based on the result of the first question, Xu You first calculated the displacement and acceleration of the second stage of motion.
Just when Xu You wanted to continue teaching the formula.
Suddenly I realized a problem.
"No, there's a trap in this question!"
That is, the final velocity of the small object cannot exceed the speed of the conveyor belt.
If you haven't noticed this problem.
It is very likely that you will make fatal mistakes and lose points on the question.
This kind of mistake is like a car reversing its speed after braking; it is very low-level but easy to make a mistake.
The main reason is that students are not proficient in problem solving and their understanding is not thorough enough.
In about twenty minutes, Xu You had finished answering all the questions.
Because Xu You started answering questions during the break, there is still half an hour left before the end of the exam.
Seeing that there was still plenty of time, Xu You used a few more minutes to check the roll of paper from beginning to end.
After making sure that all the answers are completely correct.
Xu You decided to go forward and hand in the paper.
My deskmate Dong Chao was copying Xu You's answers, but before he had finished half of them, Xu You handed in the paper.
"wait……"
Dong Chao wanted to reach out to keep her, but it was too late.
At this time, Lu Zhiyao also finished answering the paper and stood up to hand in the paper.
In previous quizzes, Lu Zhiyao was always the first to hand in her paper.
Not for anything else, just to hand in the paper earlier and start working on other questions earlier.
It was just a small test, so naturally Lu Zhiyao would not condescend to check it.
Just as Lu Zhiyao stood up to hand in the paper.
But she found a figure that was already in front of her.
Lu Zhiyao frowned slightly, looked carefully, and found that the classmate was Xu You.
Lu Zhiyao had not spoken much to Xu You, and only had a basic understanding of Xu You.
Seeing that it was Xu You, Lu Zhiyao felt relieved at once.
Xu You is the type of person who works very hard but learns very slowly.
Although Xu You's grades are relatively good in the class.
But Xu You definitely couldn't finish this roll of paper in such a short time.
There must be some problem and I want to ask the teacher.
Lu Zhiyao naturally wouldn't want to do something boring like competing with other classmates in answering speed on a quiz.
But if there really is someone in the class who can answer faster than you.
Lu Zhiyao still felt a little uncomfortable.
