# How many homes could you supply with free donuts?

Should you get a Covid-19 vaccine? Yes it will protect you and others to help us overcome this pandemic and return to a more normal life. But wait! If you get the vaccine, you can get a donut too! At least that’s the case that Krispy Kreme offers. Once you get your vaccine, you get a donut. And it’s not just a donut – it’s a everyday. That’s a lot of donuts.

OK, so how about physical estimates to go along with your gluttony?

Let’s say all Americans who have a Covid-19 vaccine get (and eat) one donut a day. Of course, eating food gives you the energy to do things – that’s how food works. So, suppose all of these humans are using that extra energy to pedal stationary bikes. All bicycles are connected to generators which supply the electricity network. What kind of power output would that produce?

The first thing we need is the number of donuts consumed per day. According to the Centers for Disease Control and Prevention, as of April 7, 63 million Americans had been fully immunized. (Don’t worry too much about the numbers – I’ll do all of my math in Python so you can change the values, if that makes you happy. I’m also going to assume that all of these people have their donuts every day.)

Next, I need to know the amount of energy per donut. According to the Krispy Kreme website, a frozen meal is 190 calories. But what is a calorie? Well, the original calorie was created to describe thermal energy changes for different substances. People later used the term to measure how much chemical energy your body can gain from eating food. However, there is a catch: for some reason all food labels say calories, but these are really. kilocalories. So, this donut has 190,000 calories. I guess it just looks too big for people to consider eating.

There is another unit of energy: the joule. Since this is the preferred unit of energy for physicists, I will use it. To convert between units, 1 calorie equals 4.184 joules.

But what does this have to do with your everyday life? Consider something you could do without too much effort. Suppose you have a textbook on the floor and take it to put it on a table. Since you are exerting a force on the book for a certain distance, you have to change the gravitational potential energy of this book. The change in gravitational potential energy is equal to the mass of the pound (about 1 kilogram) multiplied by the local gravitational field (g = 9.8 N / kg) then multiplied by the change in height (approximately 1 meter). This will give an energy change of about 10 joules. This gives you a rough idea of ​​how much energy is in a joule.

But what about power? Power is the rate of change of energy. It tells you how fast you are using energy. As an equation, it looks like this: