The centroid of the truck and the heavy object before braking is located in x₁ and x₂ respectively; After braking to a complete stop, the truck has moved for a distance of s₁, and the two centroids are located at x₁'=x₁+s₁ and x₂=x₂+s₁+L, respectively. So there is

x = Mx'₁+mx'₂ of M+m - Mx₁+mx₂ of M+m = M+m

(M+m)s₁+ML=2u₁g/v²

This leads to the following solution:

s₁ = 2 u₁ mL of v²-M + m

"Alas...... GG, the impulse theorem is a bit of a break, and there is not enough time to check it. ”

Wu Bin raised his head and let out a long sigh and rubbed his temples.

At this time, Gu Fan stretched out his head and glanced at the 40 lines of operations on the draft paper on Wu Bin's desk, and gasped; "Did I really study physics?"

"Well, you've learned, but you haven't learned this yet." Wu Bin nodded.

"Then I wish I never learned this, what is it? Semi-final questions? ”

"No, it's a sad memory."

"Snake spirit disease."

When Wu Bin returned to the classroom, the classmates originally planned to celebrate him by scattering flowers, but when they saw Wu Bin's stunned appearance, they decided to look at him quietly.

After the fourth class, Zhang Qiu ran to Wu Bin and asked: "I'm just curious about what the question of the rematch is, if you are not in the mood to say it, I will immediately flash people." ”

"See for yourself." Wu Bin handed several pieces of scratch paper to Zhang Qiu together.

"Thanks."

After Zhang Qiu finished speaking, he took the scratch paper and looked at it with a solemn expression.

"Well...... Well, well~oh~hiss......"

"Singing, you." Gu Fan, who couldn't stand Zhang Qiu's strange tone, complained.

Zhang Qiu didn't pay attention to Gu Fan, just gently put a few pieces of scratch paper back on Wu Bin's desk and left a sentence before turning away.

"Just when I ...... I didn't learn to compete. ”

This made Gu Fan amused for a moment, and said with a smile: "It turns out that I am not the only one who can't understand it." ”

"Wu Bin, don't you go for lunch." At this time, Xu Hao and Wang Qi came over and asked.

"You guys go first, I'll come later."

Xu Hao and Wang Qi glanced at each other, nodded, and didn't ask any more.

"Let's go, let's go, I heard that there is a lion's head today." Gu Fan pushed the two of them and walked out of the classroom together.

Wu Bin, who was alone in the classroom, tilted his head, closed his eyes, and fell into deep thought.

After all, it was his first time competing in a competitive competition, and his desire to win was unprecedentedly high.

What could be more fulfilling than competing for a place with others, and then breaking into the next round for a more intense battle?

'Maybe next time I'll ......'

"Hey, Wu Bin."

As soon as Wu Bin was thinking, a voice suddenly interrupted her, startling him, after all, he thought that there was no one in the class anymore.

"People are scary, scary to death, classmates." Wu Bin opened his eyes and looked at Pei Jiamin in front of him and said.

Pei Jiamin smiled embarrassedly after hearing this, "I'm sorry, I thought you heard my footsteps." ”

"Is there something wrong?" Wu Bin sat up straight and asked.

"Well, I just want to say that I admire that you can enter the semi-finals of the competition." Pei Jiamin said as she looked at the door of the classroom out of the corner of her eye, for fear that other students would turn back to the classroom like her.

Although even if a classmate came back, she only saw her and Wu Bin chatting far away, but she still felt that her heart was beating fast.

"Russia...... Actually, there is nothing to admire. ”

Hearing from Pei Jiamin's mouth that she admired herself, Wu Bin was still a little confused, why did this woman suddenly change sex?

"Actually, when I was a freshman in high school, I also thought about participating in math competitions, but the school didn't attach much importance to competitions, and I couldn't balance competitions and normal study." Pei Jiamin secretly glanced at the door of the classroom again, and after finding that there was still no one, he continued, "So when my first exam score dropped, the teacher and my mother came to persuade me to study hard and not think about competition." ”

"Huh? Has there ever been such a paragraph? ”

In Wu Bin's impression, this female student has always been at the top of the class.

"Yes, it was the middle school exam in the first year of high school, and I fell from the 8th in the grade to the 17th in the grade."

"Oh."

Wu Bin, who nodded his head and said the word "oh" with an expressionless face, only had 'hehe' at this moment in his heart! ’

Seeing Wu Bin nodding, Pei Jiamin continued: "At that time, I gave in, I gave up the competition and began to concentrate on studying, so when I heard that you broke into the semi-finals of the physics competition, I felt very admired, because you did what I didn't do."

Before Wu Bin could say anything, Pei Jiamin suddenly took out an ice cola from behind and stuffed it into Wu Bin's hand, and said, "When you have troubles, it will be more comfortable to drink some ice." ”

"Russia...... Thank you. Wu Bin felt the coldness on the Coke can and nodded.

"I believe that as long as you continue to work hard like this, you will definitely succeed."

After speaking, Pei Jiamin ran out of the classroom like a fly, her whole face flushed.

"What's the situation......" Wu Bin, who grabbed his hair, looked inexplicable.

Maybe she'...... A good guy? ’

After all, she said she admired me, ahahahaha! Looks like I'm finally getting to know how good I am. ’

After thinking about it, Wu Bin opened the pull ring of the Coke, and poured a few sips of "Gudu" and "Gudu".

"Whew...... It seems to be really comfortable, well, I'll give her a bottle tomorrow. ”

Wu Bin, who was in a better mood, slowly shook out of the classroom with a cola and walked towards the cafeteria.

……

In the next few days, Wu Bin did not slack off on the physics competition because he might not be able to enter the provincial team, but became more addicted to learning, and Gu Fan, who was so addicted to asking him two questions at noon, was not easy to speak.

Because Wu Bin exudes an aura all over his body, no one should enter, and no acquaintance should approach.

Particle kinematics, conservation of momentum, conservation of mechanical energy, conservation of angular momentum, rigid body mechanics, etc., what Wu Bin once felt he understood, he had to study again at this moment.

Just because he's not strong enough!