Work Text:
“If kinetic energy is converted to thermal energy, how hard do I have to slap a chicken to cook it?”
All eyes turned to Midoriya.
“What.. What the fuck?” asked Bakugou.
Midoriya waved his physics worksheet in the air: a half-dozen questions about conservation of energy.
“How. Hard. Do I have to slap a chicken. To cook it.”
Yaoyorozu instantly whipped out her TI-84 graphing calculator. “At a speed of 1,665 meters per second,” she responded after a moment of manic typing.
“You did that all in your calculator? You didn’t even show your work!” Kaminari whined.
As if in response, the class vice president pulled a crisp sheet of lined notebook paper out of her forearm. She commentated her work as she wrote in neat lines, making her math clear and sure to earn full credit had she been working on an actual homework problem.
“To start, we’ll use the formula for converting between kinetic and thermal energy: One-half m-v-squared equals m-c-T, where—”
“We never learned the thermal energy formula in class!” Bakugou interrupted, irate. “Why do you just know these things?!”
Yaoyorozu only smirked in response. “Oh, a little bit of light reading, I suppose.” She twirled her pencil around her fingertips and continued writing. “C in the thermal energy formula represents the specific heat of the item being heated, which happens to be 2,720 Joules per kilogram-Celsius for a standard rotisserie chicken. T is the change in temperature we want the chicken to achieve: 205 degrees Celsius, assuming the chicken starts off frozen at zero degrees.”
“Does she have the Wikipedia page for chicken memorized to the letter or something?” Kirishima muttered in mild awe.
“We’re talking about Yaoyorozu here. Probably,” Ashido chimed in.
“Using common assumptions such as the average mass of a human hand and that of a chicken, we can solve for the relevant variables using basic algebra,” Yaoyorozu continued, ignoring the other two. “V will ultimately equal about 1,665 meters per second, accounting for rounding errors.” She slid the cover back onto her calculator with a crisp click and passed her work around for the others to see.
“So, I guess that begs the question,” Midoriya replied slowly, “Who could be capable of cooking a chicken in one slap?”
The room fell silent with thought. Each of the students quietly pondered Midoriya’s question, and their attention drifted further and further away from their assignments.
“I guess Iida would be as good a candidate as any,” Uraraka suggested eventually. “Iida, what’s your top speed again?”
“I’d need nearly six thousand kilometers per hour, or around 3,700 miles per hour,” he muttered. He pushed his glasses up his nose. “I admit, that may be a bit of a stretch, but I’ve never paid much attention to my actual numbers before.”
“Actually, Uraraka, you can technically levitate yourself indefinitely, right?” Kaminari piped up. “If we just let gravity accelerate you as you slap downwards rather than to the side..!”
Yaoyorozu was quick to pick up on the blonde’s train of thought and snatched her scratch work back. “Using the fourth kinematic, velocity-squared equals velocity-initial-squared plus two-a-delta-x—” She broke off suddenly to compute the math. “She would have to fall from a distance of over 142,000 meters in the air.” Yaoyorozu appeared mildly heartbroken at the result as she shook her head. “That’s well into the thermosphere. Uraraka’s Quirk alone wouldn’t be viable here—it doesn’t help her breathe in atmospheres with little to no oxygen, survive in extremely high temperatures, not to mention protect from cosmic radiation.”
The class went back to thinking. Eventually, Asui piped up:
“Speed is just distance divided by time, though, right, ribbit?” she asked. “A teleportation Quirk might do it.”
“That’s the formula for speed , Asui,” Bakugou deadpanned. “Acceleration is.. Something else.”
“It’s the derivative of speed!” Ashido chirped, enthusiastic to contribute. “The slope of the line tangent to the velocity curve!”
“A teleportation Quirk wouldn’t even be a curve!” Bakugou roared back. “It’s just two dots! Derivative that for me!”
“Bakugou has a point,” Yaoyorozu hummed. “The derivative would be indeterminate, as you can’t differentiate endpoints.”
“.. Why are we trying to solve for acceleration again?” Aoyama asked meekly, mildly confused. “Don’t we have a kinematic that only uses velocity?”
“Delta-x equals t times the quantity of v plus v-naught over two?” Uraraka supplied hesitantly. “I.. I don’t think we have enough knowns to solve using that..”
“What the hell are we even solving for now?” Jirou asked flatly. “You’ve lost me.”
“Teleportation Quirks, ribbit,” Asui replied. “Velocity should be infinity, because time is zero.”
“But that trivializes the entire problem,” Yaoyorozu said, patient yet slightly disappointed at the prospect of such an interesting physics question going unsolved. “Also, regardless of time being zero, the distance the individual travels with their Quirk is highly variable; we can’t say anything about the value of delta-x—”
“How is that any different from Iida choosing to run five steps or across the continent?!” Bakugou rebutted.
“.. Aren’t we trying to slap a chicken? Teleporting.. Wouldn’t make them.. Slap faster..” Sero slowly provided. “Context, guys.”
The group hushed, a little embarrassed at their blunder.
“I could cook the chicken with my flames,” Todoroki offered finally.
“ We’re talking about slapping it, Todoroki! ” Bakugou hollered. “You may as well ask Yaoyorozu to build us an oven!”
“Wait,” Shoji interrupted. “The hand’s mass has a direct relationship with the amount of energy transferred to the chicken. Meaning if the hand were larger, velocity wouldn’t need to be as high. What if..?”
Yaoyorozu hummed thoughtfully. “If you slap at a velocity of 11 meters per second—the average slap speed—you’d need a hand with a mass of..” She returned to her graphing calculator. “9,217 kilograms.”
“Oh.” Shoji’s face fell.
“Then assume we’re using a larger chicken!” Kaminari suggested. “If the target’s too small relative to the hand, just make the target bigger!”
“That’d increase the chicken’s mass and work against us,” Iida responded simply. “Unless you’re suggesting to increase only its volume, and not its mass..?”
“That’s density!” Ashido chimed in.
“You guys seriously think the chicken’s size is the problem?” Bakugou deadpanned. “Talk about Shoji making us a nine-thousand-kilogram hand first.”
“Hold on.. Just for the sake of the argument, couldn’t we branch out to using other forms of energy to cook the chicken?” Kouda tried. “Other than heat, of course. Sorry, Todoroki.”
“Then we could consider Jirou and Kaminari as candidates to cook the chicken,” Yaoyorozu responded dutifully. “But sound energy is very inefficient in this regard, and electric current.. Hmmm.” She tapped her chin with her eraser a few times before pulling out her phone to do some research.
“Using a rotisserie chicken as a resistor.. That’s new,” the blonde snorted.
“Actually, I’d like to go back to the idea of using Uraraka’s Quirk, please,” Midoriya chimed in.
“You have a new idea?” Yaoyorozu piped up as she looked away from her phone.
“It should be easy enough to calculate the speed at which objects travel after she levitates them, right? Just time her levitating things, say, ten meters and do some math. Like a lab.” The class nodded, intrigued at where Midoriya was going.
“We also know the required distance between Uraraka and the chicken: 142 thousand meters, approximately. Therefore, we could divide to find the length of time it would take for the chicken to reach that height, right?” The class nodded in agreement. “So, if we have her touch a chicken, wait for that duration, then cancel her Quirk, the chicken would fall, and it would have the same effect as Uraraka falling that same distance to slap the chicken without her needing to travel into whichever layer of the atmosphere that was, because acceleration due to gravity is independent of item mass!”
The students unanimously took on an air of enlightenment as they considered Midoriya’s proposal.
“So, do we treat the entire earth as the ‘hand’ that slaps the chicken and recalculate with that assumption, then?” Kirishima asked. “Or do we have a sacrifice stand under the chicken with their hand outstretched?”
“The chicken won’t even survive the damn fall regardless,” Bakugou spat. “Or it’ll burn up on re-entry anyways. Think it through next time.”
“I still think it’s worth a shot,” Yaoyorozu suggested. “We have no better ideas, and there’s no harm in just letting it fall to the ground for the sake of science. There won’t even be any food waste, because Kouda can feed the scraps to the animals.”
She grinned and clapped her hands together. “Well, I think we’re all free this weekend, so it looks like we have a plan! I’ll be back tomorrow with a rotisserie chicken!”
At eight A.M. that Saturday morning, Aizawa woke up against his will and, mug of coffee in hand, trudged through the hallways only to stumble into Class 1-A watching Uraraka Ochako levitate a rotisserie chicken up to an indoor balcony, with their vice president dangling a measuring tape from the railings.
He turned on his heel, returned to his room, and went back to sleep.
When Ectoplasm looked through Class 1-A’s homework folder to find a vast majority of them having not done their homework that weekend, he couldn’t help but question whether he had taught something unclearly.
“I’m aware that this is a mathematics class, but given its strong ties with physics, I thought it only prudent to teach a mini-lesson on basic physics concepts—But evidently, I have not taught it well. Please, tell me what you find confusing,” he encouraged kindly.
Yaoyorozu raised her hand. “Actually, Ectoplasm-sensei, I don’t think there is anything wrong with your teaching. Your worksheet simply raised a question that we tried to answer on our own.. But we lost track of time in the process,” she admitted sheepishly.
That piqued Ectoplasm’s curiosity. “Oh? Please, do tell me what this question is. I will try my best to answer.”
“If kinetic energy is converted to thermal energy, how hard do I have to slap a chicken to cook it?”