Geek Physics: Surprising Answers to the Planet's Most Interesting Questions

Geek Physics: Surprising Answers to the Planet's Most Interesting Questions

by Rhett Allain

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Product Details

ISBN-13: 9781118360156
Publisher: Turner Publishing Company
Publication date: 04/14/2015
Series: Wiley Pop Culture and History Series , #6
Edition description: Second Edition
Pages: 224
Sales rank: 1,317,760
Product dimensions: 6.00(w) x 8.90(h) x 0.40(d)

About the Author

Rhett Allain an Associate Professor of Physics at Southeastern Louisiana University and a popular Dot Physics blogger at Wired Science Blogs. He has a knack for explaining things in a way that is both entertaining and useful. He is also the author of the National Geographic book Angry Birds Furious Forces: The Physics at Play in the World's Most Popular Game and of Just Enough Physics. He lives in Louisiana.

Read an Excerpt

How much does R2-D2 weigh if he can fly?



Let me start with a quiz question.



In Star Wars Episode II: Attack of the Clones, R2-D2 shows that he can fly. What is wrong with a flying R2-D2?

a) Nothing. This is the way that George Lucas would have wanted it in the original Star Wars but he couldn’t digitally render a flying R2 with a Commodore 64*.

b) If R2 can fly, why didn’t he do this in the original trilogy?

c) He wouldn’t fly that way.

d) Droids shouldn’t be allowed to fly.



And here you see that this is really a trick answer for choice a. Why? Because the Commodore 64 didn’t come out until 1982 and Star Wars (it was just called Star Wars then) came out in 1977. So, choice a) can’t possibly be correct.

The correct answer is c). He wouldn’t fly that way. But how does he fly? If you watch the movie carefully, you will see that while R2 is flying (all his close friends just call him R2 and not his full name of R2-D2), he looks like this.

This is a flying R2 while he is moving at a constant speed. You might think: well, what is wrong with this? It looks perfectly fine, right? I think this is the real issue right here. R2 is shown to fly the way people think about forces and motion, so there is no real problem.

Ah, but now we are talking about forces and motion. Let me start with two experts in this field: Aristotle and Isaac Newton.

According to Aristotle, what does a constant force do to an object? For him, constant force means constant motion. Honestly, to most people this idea just makes sense. It is really easy to agree with Aristotle, even if he is speaking in Greek. Doesn’t this idea of forces always seem to work? If I push a book on a table, the book moves. If I push harder, it moves faster. If I stop pushing the book, the book stops. Seems simple.

For Aristotle, R2-D2 flies as he should. If he wants to fly at a constant speed, he needs to angle these thrusters back a little. This way, part of the thrust pushes down to keep him up and part pushes back to move him forward.

Now, what about Newton? Well, it’s not just Newton that came up with a better idea about force and motion. It’s just that people call them “Newton’s Laws” of motion. The Newtonian idea of force and motion is that forces CHANGE the motion of an object. Change is the key word here. If you have a constant force on an object, it would constantly change its motion. This means that it could keep increasing in speed with a constant force.

Consider the following example. A bowling ball is sitting on a smooth bowling alley. If you give it a little push, it will start to move. It will keep rolling for a while, but will eventually stop. This is because there is another small force on the bowling ball that most people tend to forget about: friction. So after the push, there is just one force acting on the ball to make it slow down. However, if you ran along behind it, you could keep giving it little pushes to keep it going the same speed, balancing the frictional force. If you used a really long stick to keep applying a continuous level of force that was greater than the frictional force, it would go fast and faster.

Suppose there was a way to remove ALL forces from a moving object. For such an object, the speed would stay constant. I know this is hard to image because everything we see on this Earth has some type of frictional force on it.

Okay, so if you look at the way R2 flies, it seems to agree with Aristotle and probably 90% of the human population. But, is there any way to make this flying R2-D2 agree with the Newtonian ideas of force and motion? In other words, in what situation would this type of flying agree with Newtonian physics?

Air resistance is our best bet. Suppose there is non-negligible air resistance force on the flying R2. In this case, he would have to have his thrusters angled back to balance the horizontal air resistance. We can actually use this to figure out how much R2 weighs. If we know what the air resistance and his speed is, we can figure out how much thrust he is putting out. If we know how much thrust he putting out, we can figure out how much he must weigh for that thrust to lift him.

Table of Contents

How Fast Do Tweet Waves vs. Seismic Waves Travel?

How Much Would R2-D2 Weigh If He Could Fly?

How Realistic Is the Physics in Angry Birds?

Big Space Ships With Even Bigger Thrusters

Jumping Off a Building With Bubble Wrap

Is It Better to Crash Into Another Car, or a Brick Wall?

Can a Human Out-Pull a Truck?

Would the Hulk Break the Road Whenever He Jumped?

Can Humans Fly Like Birds, With Wings?

Can You Fall Faster Than the Speed of Sound?

Big Hail Is Bad

Why Do Astronauts Feel Weightless?

How Can a Broom Balance On Its Brushes?

Can You Cook a Turkey By Dropping It?

How Much Energy Does It Take to Get a Candy Bar in Orbit?

Building and Supplying a Death Star With the ATV

The Long Jump: Gravity and Air

Linear Regression and the Long Jump

Power and Olympic Swimmers

Scoring the Decathlon

Diving and the Moment of Inertia

Could Cyclists Cheat With Hidden Batteries?

What is Arnold Schwarzenegger Made Of?

What Does Pi Have to do With Gravity?

Can Airplanes Save Fuel by Using iPads?

How Many Zombies Could You Drive Through?

How Much Water Would It Take to Move a Car?

Could Adam Savage Have Accidentally Killed Himself in the Swimming Car Myth?

A Scale at the Bottom of a Pool

Spaceships Underwater

How Much Ice Do You Need to Cool Your Beer?

Can Ice Cream Get Cold Enough to be Zero Calories?

The Power Source for a Light Saber

Can You Charge Your Phone by Typing?

Why Do Mirrors Reverse Left and Right, But Not Up and Down?

Can a Building Be a Sun-Death Ray?

Gollum Physics

The Physics of Thor’s Hammer

A Banana Powered Generator

How Many Dollar Bills Would it Take to Stack Them to the Moon?

Could You Build a Scale LEGO Model of the Death Star?

Would You Rather Fight a Horse-Sized Duck or 100 Duck-Sized Horses?

NASA Space Games

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