estimation
What Happens If a Space Elevator Breaks
These structures are a sci-fi solution to the problem of getting objects into orbit without a rocket—but you don’t want to be under one if the cable snaps.
By Rhett Allain
The Physics of Wile E. Coyote’s 10 Billion-Volt Electromagnet
The famous cartoon schemer has an ingenious plan to lure Bugs Bunny out of his hole—and it involves a giant magnet and an iron carrot.
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The World Is Messy. Idealizations Make the Physics Simple
Even ordinary actions, like tossing a tennis ball, can be extraordinarily complex to calculate. The trick is knowing what to leave out.
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Can Your Gravitational Pull Affect Your Game of Pool?
It’s hard enough to predict the outcome of ball collisions in a game of billiards. Do you also have to factor in a player’s effect on the cue ball?
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Will Nathan Drake Make This Jump in the Uncharted Trailer?
Leaping into an airborne cargo plane might not be impossible, but the numbers have to work out just right.
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Could MJ Really Hang on During Spider-Man’s Swing?
Shooting a web from your hands requires Spidey powers. But does keeping your grip on one of them require Spidey strength?
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You Can Measure This Fundamental Quantum Constant Using LEDs
Planck’s constant helps us understand atomic-sized things. One of the best ways to grok it is through this experiment involving different colors of light.
By Rhett Allain
Could the Moon Actually Crash Toward Earth?
The trailer for the film Moonfall shows our satellite getting too close for comfort. Here are the physics of what it would take to push the moon out of orbit
By Rhett Allain
Would the Free Guy Inflatable Bubble Protect a Real Person?
In the movie’s video game world, a whole-body airbag protects Ryan Reynolds as he falls off of a building and onto a car. Would that … work?
By Rhett Allain
How Did People Find the Fundamental Charge With Drops of Oil?
Back in 1909, figuring out the charge of a single electron was a Nobel-worthy pursuit. Today, it’s a good lesson in understanding four key forces.
By Rhett Allain
How to Prepare for the Robot Apocalypse (If You’re a Robot)
In the Netflix show The Mitchells vs. the Machines, robots are planning to blast all of humanity into outer space. How much time and energy will that take?
By Rhett Allain
You Need to Weigh Some Water. All You’ve Got Is a Paper Clip
OK, so you might need a couple other supplies, but your best option is to do what MacGyver would do: Turn it into a scale.
By Rhett Allain
Could Bad Guys Actually Escape Falcon in a Wingsuit for Two?
In The Falcon and the Winter Soldier, a villain straps a hostage to his wingsuit and leaps off a plane. Cue the action—and the fun physics.
By Rhett Allain
How Many Homes Could You Power With Free Doughnuts?
Should you get a COVID vaccine? Yes, it will protect you AND protect others to help us move past this pandemic so we can get back to a more normal life. But wait! If you get vaccinated, you can also get a doughnut! At least that's the deal that Krispy Kreme Doughnuts is offering. Once you get your vaccine, you get a doughnut. Oh, it's not just one doughnut—it's one doughnut every day. That's a lot of doughnuts.
OK, so how about some physics estimations to go along with your tasty doughnut?
Let's say that all the Americans that have a COVID vaccine get (and eat) one doughnut a day. Of course eating food gives you energy to do stuff—that's how food works. So, suppose that all these humans eat their doughnut and then use the extra energy to peddle a stationary bike. All of these bikes are then connected to generators so that they feed into the power grid. What kind of power output would this produce?
The first thing we need is the number of doughnuts a day. According to the Center for Disease Control (CDC) 63 million Americans have been fully vaccinated so far (as of April 7 2021). Oh, don't worry too much about the numbers—I'm going to do all my calculations in python so that you can change the values if that makes you happy. I'm also going to assume that all these people get their doughnut—every day.
Next, I need to know the amount of energy per doughnut. According to Krispy Kreme's site, a plain glazed doughnut is 190 Calories. But what the heck is a Calorie? Well, [the original calorie was created to describe changes in thermal energy for different substance](https://en.wikipedia.org/wiki/Calories. Then, later people used it to measure the amount of chemical energy your body can get from eating food. However, there is a problem. For some reason, all food labels list stuff in Calories—but these are really kilocalories. So, that doughnut has 190,000 calories. I guess it just sounds like it's too big of a number for people to consider eating.
There is another unit of energy—the joule. Since this is the preferred unit of energy for physicists, I'm going to use it. To convert between units, 1 calorie is equal to 4.184 joules. But what does this have to do with your everyday life? Let's consider something you might do without too much effort. Suppose you have a textbook on the floor and you pick it up to put it on a table. Since you are exerting a force on the book over some distance, you have to change the gravitational potential energy of that book. The change in gravitational potential energy is equal to the mass of the book (about 1 kilogram) multiplied by the local gravitational field (g = 9.8 N/kg) and then multiplied by the change in height (about 1 meter). This will give a change in energy of about 10 joules. So that gives you a rough feeling for the amount of energy in a joule.
But what about power? Power is the rate of energy change. It tells you how fast you use energy. As an equation, it looks like this:
defpower
In this expression, if ΔE is the change in energy in units of joules and Δt is the time interval in seconds then the power will be in units of watts. We are almost ready to calculate the vaccine doughnut power. We just need one more estimation—the efficiency. When a human eats a doughnut, only some of the chemical energy goes all the way into useful energy. Also, with a stationary bike generator some of the energy the human uses to push the pedals also goes into heating up some of the moving parts. In the end, only a percentage of the energy goes into electrical energy. This percentage is the efficiency. I'm just going to make a rough guess that the process of doughnut eating to electrical energy is 25 percent efficient. That's it. I just need to take the number of doughnuts per day and convert that energy to joules and then divide by the length of a day (in seconds). Oh, and multiply by the efficiency. Here's what I get. Note: this is actual python code. You can see my calculations and even change them if you like.pythonpower
You can see that for each human, it's just a measly 2 watts of power. That's around the power output for a smart phone (power values vary based on use). However, once you include all the vaccinated people we get up to 144 Megawatts. In 2019, the average household power was about 1200 watts. That means that you could use all these doughnuts to run 120 thousand homes. Oh, AND you get vaccinated—that's a win.More Great WIRED Stories
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By Rhett Allain
How Strong Is King Kong? And Could He Even Stand Up?
In physics, big things are not like small things. Here's what that means for a giant gorilla.
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The Physics of That Spinning Hug in Dua Lipa’s Music Video
The dance move seems to defy gravity—but it actually involves Newton’s second law, equilibrium, and a fake force.
By Rhett Allain
How to Free the Ever Given—Using Buoyancy Force!
Sure, you could dig the massive ship out of the Suez Canal. Or you could calculate how many containers you’d have to remove to make it light enough to float again.
By Rhett Allain
How Far Away From Perseverance Did the Descent Stage Land?
The rocket lowered the rover onto the surface of Mars before it shot away from the landing site. So where did it end up?
By Rhett Allain
How to Calculate the String Angle of a Kite vs. a Balloon
It's a beautiful day to go outside with a kite or a balloon, and compute how wind speed alters their flight.
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How Long Would It Take for a 747 to Stop, Like in Tenet?
The airplane in the movie is stripped down and doesn't have all of its brakes installed, making the calculations even more fun.
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How Would Deadpool Jump Into a Moving Vehicle?
Our sardonic superhero needs to get the timing just right to crash through the sunroof and beat up the bad guys.
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What Would Happen If All the Antarctic Ice Melted?
It … let's just say it would not be good. Here, let's do the math.
By Rhett Allain
How Much Power Does It Take to Do the Red Bull 400 Hill Run?
400 meters. A 37-degree incline. Turns out humans are capable of superhuman power outputs—if only for a short time.
By Rhett Allain
Trump’s New Space Force Missile Might Be Too ‘Super-Duper’
To go that fast, it would need a ridiculous amount of fuel—and even then, it might never come back down.
By Rhett Allain