heartbeat
The rain in May always comes unexpectedly.
The day before the preliminary round of the physics competition, the evening sky was suddenly dyed dark, and the strong wind blew raindrops as big as beans, hitting the glass windows of the teaching building hard, making crackling sounds.
The originally noisy corridor suddenly became quiet, with only the sound of rain and the faint sound of turning pages coming from the classroom.
Xu Yang and Lu Jinyu stayed in the empty physics laboratory and reviewed the key points of the competition one last time.
A thick stack of past exam questions lay on the lab table, next to it were draft papers filled with force analysis diagrams drawn by two people, and a disassembled old alarm clock - that was the teaching aid that Lu Jinyu brought from home specifically in order to understand simple harmonic motion.
"I'm still a little confused about the period formula for this simple pendulum."
Lu Jinyu scratched his head and pointed to T=2π√(L/g) on his draft paper. He asked, "Why is the period only related to the pendulum length L and the acceleration due to gravity g? Why doesn't the mass m have any effect?"
Xu Yang put down the pen in his hand and picked up the pendulum taken out of the old alarm clock - a small metal ball tied with a thin wire.
"Look at this," he said, gently pushing the pendulum, setting it swinging in the air, "we can use Newton's second law to deduce this."
As he spoke, he quickly wrote down the derivation process on the draft paper:
"The restoring force of a simple pendulum is the tangential component of gravity, F = -mgsinθ. When the pendulum angle is very small, sinθ ≈ θ, so F ≈ -mgθ. According to Newton's second law, F = ma, we get ma = -mgθ, which means a = -gθ."
Lu Jinyu leaned over and stared at the formula on the draft paper, his eyes full of seriousness:
"And then? a is the acceleration, and it's related to the displacement x, right?"
"Right," Xu Yang nodded, pointing to the swinging metal ball. "Displacement x = Lθ, so θ = x/L. Substituting that into a = -gθ, we get a = -(g/L)x. This is a differential equation for simple harmonic motion. The standard form is a = -ωx. By comparison, we know that ω = √(g/L)."
He paused and added:
"The period T = 2π/ω, so T = 2π√(L/g). You see, the mass m is eliminated in the derivation, so the period is independent of mass. Just like Galileo's Leaning Tower of Pisa experiment, objects of different masses fall at the same speed, and the same principle applies here."
Lu Jinyu suddenly realized and slapped his forehead:
"I see! That's how it is!"
He picked up a pen and rewrote the derivation on a piece of scratch paper, this time quickly and accurately. "Thank you, boyfriend. Every time you talk about it, I feel like my mind suddenly becomes clear."
Xu Yang looked at his excited expression and couldn't help but smile slightly.
He reached out and rubbed Lu Jinyu's hair - this action has become very natural now.
"Our classmate Lu is making rapid progress. He will definitely have no problem competing in tomorrow's competition."
Lu Jinyu's ears turned slightly red, but he didn't avoid it. Instead, he looked up and smiled at Xu Yang, his eyes sparkling like stars:
"That's because of you, the 'super teacher'."
At this moment, the rain outside the window suddenly became heavier, a flash of lightning streaked across the night sky, followed by a rumbling thunder.
The lab lights flickered, then snapped out.
"Oops, the power is out!"
Lu Jinyu subconsciously leaned closer to Xu Yang, with a hint of subtle nervousness in his voice.
Xu Yang was also a little surprised. He fumbled to take out his cell phone from his pocket and turned on the flashlight function.
The faint light illuminated a small area around the two people. Lu Jinyu's face appeared particularly clear in the light and shadow, and his long eyelashes trembled slightly.
"Don't be afraid, it's probably a temporary power outage caused by the heavy rain, it will be restored soon."
Xu Yang comforted him. He could feel that the person next to him was a little tense, so he patted his shoulder gently.
Lu Jinyu nodded, but still did not move away, instead he whispered:
"I'm a little afraid of the dark... and thunder."
Xu Yang was stunned for a moment, then he understood. He remembered what Lu Jinyu had said in the library last time. When he was a child, there was no one at home when there was thunder, and he hid in the closet and cried for a long time.
"It's okay, I'm here with you."
Xu Yang's voice was very gentle.
"We can talk about something else to distract ourselves."
"What are you talking about?"
Lu Jinyu's voice was muffled, like a frightened kitten.
"Let's talk...let's talk about the first time you were punished to stand in the corner?" Xu Yang suggested.
Lu Jinyu thought about it and couldn't help laughing:
"I remember that time, I was standing outside the physics teacher's office as punishment because I was secretly playing with a light-emitting diode during class, and it short-circuited and blew the fuse. You came over with a stack of homework books and even pleaded with the teacher on my behalf."
"I remember that, too."
Xu Yang also laughed.
"You had your head down, your hair messy, like a little lion who had done something wrong. It was quite cute."
"cute?"
Lu Jinyu raised his head, his eyes sparkling in the light of his phone.
"You think I'm cute?"
Xu Yang's heart suddenly skipped a beat. He looked at Lu Jinyu's face so close to him and could clearly smell the faint scent of orange soda on him.
"Um."
He whispered,
"My boyfriend is cute."
At this moment, another flash of lightning, brighter than the previous one, instantly illuminated the entire laboratory.
Xu Yang clearly saw that Lu Jinyu's cheeks instantly turned red, like a ripe apple. Then, Lu Jinyu suddenly reached out and gently grasped Xu Yang's wrist.
Xu Yang's body stiffened, then relaxed.
He could feel the warmth of Lu Jinyu's palm, and the slight trembling.
He didn't say anything, just shook her hand gently and moved the phone closer between them to make the light brighter.
"Xu Yang," Lu Jinyu's voice was very soft, with a hint of hesitation and a hint of expectation.
"After the competition tomorrow, shall we... shall we go to the movies? That new sci-fi movie about interstellar travel, it's said to contain a lot of physics."
Xu Yang's heart skipped a beat. He looked at Lu Jinyu's nervous and expectant eyes and nodded vigorously.
"Okay, I want to see that movie too."
After receiving a positive answer, Lu Jinyu's eyes lit up instantly, like the sun after the rain, dispelling the haze brought by the power outage and thunder.
"Very good!"
He said happily.
"Then we'll go after the exam tomorrow afternoon. I'll buy the tickets in advance!"
"Um."
Xu Yang smiled and nodded, his heart seemed to be filled with something warm and sweet.
At this moment, the lights in the laboratory suddenly lit up, and the pale fluorescent light instantly illuminated the entire room.
Both of them were stunned for a moment, then let go of each other's hands a little embarrassedly, but the tips of their ears turned red at the same time.
"The phone is ringing."
Lu Jinyu whispered, picked up the exam question book on the table, pretended to flip through it seriously, but couldn't read a single word.
Xu Yang also picked up his book, but couldn't help but secretly glance at Lu Jinyu.
The boy lowered his head, his long eyelashes cast a small shadow under his eyelids, but the corners of his mouth couldn't help but rise slightly.
"It's getting late. We should go back. We have to get up early to participate in the competition tomorrow."
Xu Yang closed the book and said.
"good."
Lu Jinyu also packed up his things, and the two of them walked out of the physics laboratory together.
There was no one in the corridor anymore, only the sound of rain continued.
The two walked side by side, no one spoke, but the atmosphere was particularly warm. When they reached the door of the teaching building, Lu Jinyu suddenly stopped and said:
"Xu Yang, wait a moment."
Xu Yang turned around and looked at him in confusion.
Lu Jinyu took out an umbrella from his schoolbag and handed it over:
"It's still raining heavily outside, so you should take an umbrella. My home is close to school, so we can just run back."
Xu Yang looked at the blue umbrella with small star patterns printed on it, which was very cute.
"No need." He declined.
"I can run back too. You can keep the umbrella for yourself."
"no."
Lu Jinyu stubbornly stuffed the umbrella into his hand.
"You'll catch a cold if you get caught in the rain, and we have a competition tomorrow. Be good and take it."
Xu Yang looked at his serious expression, and felt warm in his heart, so he had no choice but to take the umbrella:
"Okay then, thank you, boyfriend. I'll return the umbrella to you tomorrow."
"Yeah!" Lu Jinyu nodded, smiled at him, then turned and rushed into the rain.
Xu Yang stood at the door, watching Lu Jinyu's running back until he disappeared around the corner.
He opened the blue umbrella and walked into the rain.
The star pattern on the umbrella sparkled under the street lights, just like Lu Jinyu's eyes.
After returning home, Xu Yang hung the umbrella at the door and sat at the desk, but did not review immediately.
He remembered the warmth of Lu Jinyu's hand holding his wrist in the laboratory just now, and the expectant look in his eyes when he invited him to see a movie, and his heart couldn't help but beat faster.
He took out his phone, opened the chat box with Lu Jinyu, and typed a line of words:
"Thank you for your umbrella today, and thank you for...keeping me company."
After thinking about it, I felt it was a bit corny, so I deleted the second half of the sentence and only sent the first half.
After a few seconds, Lu Jinyu replied:
"You're welcome! Take good care of your umbrella, and see you tomorrow!"
A smiley face emoticon was added at the end.
Xu Yang looked at the phone screen and couldn't help laughing.
He put his phone aside and picked up the collection of real competition questions, but found that his attention was particularly focused. The knowledge points that he had found difficult to understand before, he now understood them after reading them once.
He knew that this was not only because he had reviewed thoroughly, but also because he had a certain power in his heart that supported him and made him full of confidence.
The next morning, the rain had stopped, the sky was clear, and the warm sunlight streamed into the room through the window.
Xu Yang packed his things, took the blue umbrella, and went out to school.
When he arrived at the entrance of the examination room, Lu Jinyu was already waiting for him there.
He wore a white T-shirt and jeans, looking fresh and energetic.
Seeing Xu Yang coming over, he immediately waved and greeted:
"Xu Yang! Here!"
Xu Yang walked over and handed him the umbrella:
"I'll give you the umbrella back."
"good."
Lu Jinyu took the umbrella and put it in his schoolbag, then took out a chocolate from his pocket and handed it to Xu Yang.
"Here, to replenish your energy. I wish you good grades in the exam!"
"Thank you, you too."
Xu Yang took the chocolate, peeled off the candy wrapper and put it in his mouth.
The sweet chocolate spreads on the tip of the tongue, and my heart feels sweet too.
“Let’s cheer together!”
Lu Jinyu raised his fist and said.
“Let’s do our best!”
Xu Yang also raised his fist and bumped it lightly with his.
The bell for the examination room rang, the two looked at each other, and then walked into the examination room together.
The exam questions are very difficult and involve a lot of difficult knowledge from the competition, such as the introduction to relativity, the foundation of quantum mechanics, the application of the second law of thermodynamics, etc.
Xu Yang answered the questions calmly. When he encountered something he didn't understand, he thought of Lu Jinyu's serious look yesterday and the scene of the two of them reviewing together, and he was suddenly filled with strength again.
He could feel that his physics level had improved greatly during this period, not only because of his hard work in reviewing, but also because of Lu Jinyu's company and encouragement.
When the bell rang to signal the end of the exam, Xu Yang breathed a sigh of relief.
He put down his pen and looked at Lu Jinyu next to him, and found that he was also looking at him with a relaxed smile on his face.
"How did you do on the test?"
After walking out of the examination room, Lu Jinyu immediately asked.
"It's okay. I can answer most of the questions. The last question on relativity is a bit difficult. I'm not sure if I answered it correctly," said Xu Yang.
"Me too!" Lu Jinyu felt the same way.
"I always got time dilation and length contraction mixed up in that question, so I managed to write down an answer. But it doesn't matter, the test is over anyway, so let's not think about it for now!"
He paused, his eyes full of anticipation again:
"By the way, I've already bought the movie tickets for the 3pm show. Let's go get something to eat and then go to the cinema, shall we?"
"Okay." Xu Yang nodded with a smile.
The two of them walked out of the school together, slowly strolling along the street. The sun was shining brightly, the breeze was gentle, and the flowers along the roadside were blooming extraordinarily brightly.
"Xu Yang," Lu Jinyu suddenly stopped and looked at Xu Yang seriously.
"No matter what the result of this competition is, I am very happy because I have been able to review and discuss problems with you during this period. I feel very fulfilled and I have learned a lot."
Xu Yang looked at his serious eyes and felt a ripple in his heart.
He mustered up his courage and gently held Lu Jinyu's hand:
"Me too, Lu Jinyu. I also feel very happy when I am with you."
Lu Jinyu's body stiffened, then he held Xu Yang's hand, their fingertips tightly clasped together.
The two did not speak, but just looked at each other quietly. The sunlight shone on them, warm and beautiful.
At the entrance of the cinema in the distance, a huge poster was printed with scenes of interstellar travel, as if inviting them to embark on an unknown journey together.
Xu Yang knew that no matter what difficulties and challenges he would encounter in the future, as long as Lu Jinyu was by his side, he would have the courage to face everything.
Because their heart rates have become consistent without them realizing it.
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