Under the leadership of the physical education teacher, Yi Cheng followed the other students to do warm-up exercises, and then silently went to the shallow water area.

is completely different from him, Bai Jingxue is quite talented in swimming, if it weren't for her good development, she would have been recruited into the school swimming team a long time ago.

watched Bai Jingxue jump on the three-meter springboard.

Yi Cheng couldn't help but wonder if she was a little older again.

There is not so much to worry about, Yi Cheng now just hopes to end the swimming lesson quickly and return to the classroom to study hard.

He stepped on the floor of the pool, moving carefully.

There were dozens of landlubbers moving like him.

The swimming teacher on the side kept a close eye on these people's every move, as long as they didn't die on their own, it was not much of a problem.

In order to ensure safety, there will be 3 swimming instructors and 2 lifeguards.

Swimming instructors also teach different levels of people.

People like Bai Jingxue belong to the objects of key care.

More people looked at Bai Jingxue with envy and excitement.

Thump!

Xiaobai plunged into the deep water with a very standard entry position, and the splash was very beautiful.

Yi Cheng glanced at it, paddling slowly on his own.

It's also strange to say.

Today felt completely different from before, his body rose and fell with the water, his toes moved with it, and there was an urge in his heart to take off at any moment.

I don't know why, but he was especially eager to really let go of his hands and feet today.

And this urge is getting stronger and stronger.

Yi Cheng suddenly realized-

That's because he got [Swimming Skill Lv1].

"You try to put your feet up."

A pleasant voice came to my ears.

Yi Cheng looked up.

In his sight, a mature, beautiful, and dignified face appeared.

Math teacher Ran Bingqing.

It is the math teacher who is said to love him and teach him like his own son.

Of course, Yi Cheng did not disappoint her, and her math scores continued to dominate the top three in the whole grade.

Teacher Ran, dressed in black dead reservoir water, squatted on the edge of the pool and smiled at him.

Yi Cheng suddenly remembered that she was also a well-known swimmer when she was young, and her swimming skills were even better than the regular physical education teachers in the school, so sometimes when she was not busy with her classes, she would occasionally come to replace a few swimming lessons.

Yi Cheng quickly turned his head to the side.

Although Ms. Ran is in her 30s, her figure and skin are well maintained, if it weren't for the fact that she was her math teacher, he would probably only think that the other party was a college girl in her early 20s when she walked on the road.

"Do you know why objects float on the water?" Teacher Ran did not have any difference between teachers and students, and asked patiently and kindly.

Yicheng adjusted back to his state and entered the learning mode.

Ms. Ran is a good teacher who can always give him very strong guidance in learning.

"Because of the density?"

He looked up at the teacher, "What is less dense than water will float on the water." ”

"Are you less dense than water, then?" Teacher Ran smiled and bent his eyes into crescents.

"Definitely not."

Yi Cheng's toes could still touch the bottom plate, and if the density was less than the water, he would have floated up long ago.

"Is it pressure, then?" Yi Cheng recalled what Teacher Ran had just told him and raised his feet.

In this way, the contact surface between himself and the water surface will increase, and the average pressure will be smaller, and the water surface will be able to lift him?

Teacher Ran smiled slightly.

"A little. But this knowledge is not in high school. ”

"......" is not actually high school knowledge.

"Is it math then?" Yi Cheng suddenly became interested, and his eyes lit up.

"Of course." Teacher Ran sat on the edge of the pool and hung her legs in front of him.

"You know, everything is number," she looked into Icheng's eyes calmly and gently, "in fact, the essence of the principle of swimming is fluid mechanics and Newton's second law. ”

"Fluid mechanics?" Yi Cheng's eyes twinkled.

"Bernoulli's equation is at the heart of fluid mechanics."

She gestured with her fingers in the air, "p+(1/2)*ρv ^2=constant (p0), and the terms are called static pressure, dynamic pressure, and total pressure."

As the velocity increases, the pressure decreases. When the velocity decreases, the pressure increases; When the speed drops to zero, the pressure reaches its maximum.

Just like the lift force generated by the wing of an airplane, the lower surface velocity is low and the pressure is strong, and the upper surface velocity is high and the pressure is small, so the resultant force is upward.

To put it figuratively, when you are paddling on the surface of the water, the speed of the water around the body increases due to the impetus generated by the upper layers, and the flow speed of the water below is slower, resulting in unequal upward and downward pressure, which gives you lift, which is why in still water, if you also stay still, you will sink anyway.

But once you get moving, you'll float the cause. ”

"I see." Yi Cheng nodded.

It's better to be a math teacher.

Before, the PE teacher would only teach him to bury his head in it and adjust his posture, but how can you learn to swim if you don't understand the principle?!

"Also, because you give the water a force, it also gives you a reaction force, and the reverse force pushes your body forward and gains speed, so the harder you paddle backwards, the stronger the speed boost and lift you get. That's the basics of swimming.

And burying your head and lifting your feet up is to make you have less resistance when moving forward and swim faster. ”

Teacher Ran smiled, "Do you understand?" ”

"Understood."

Yi Cheng nodded vigorously.

Teacher Ran smiled with relief and retracted her feet to the shore.

She clasped her hands and looked at Yi Cheng calmly.

"Go ahead. All you need now is courage. ”

Yi Cheng nodded, buried his head in the water, and then slashed hard......

Two minutes later, Ran Bingqing's eyes widened in surprise.

……

"Come on!! Less than 30 meters! "The swimming coach was there to cheer the students on.

Fan Yun, a young swimmer he likes, is paddling hard, and he is now practicing swimming at a freestyle speed.

The 100m standard for national second-level athletes is 1 minute 05 seconds.

Fan Yun's best time was 59.13 seconds.

He was in good shape today, and he was much faster than before for most of the swim.

"Come on, 20 ...... more"

The coach's voice got stuck in his throat, and he involuntarily stood up.

If before he hadn't had time to notice, or if it was just an illusion, now, he saw very clearly and clearly—

A student who has never been in the impression of a senior in high school, swims from one end to the other in a shallow pool at a breakneck speed.

Visually faster, it is faster than Fan Yun.

"Oh my God, where did this guy come from?"