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Build an 'Impossible' Wind-Powered Car

Abstract

Is it possible for an entirely wind-powered vehicle to travel directly downwind faster than the wind? This might seem counterintuitive or like it would violate the law of conservation of energy. After all, any good scientist knows that perpetual motion machines are impossible. However, as demonstrated by YouTubers Rick Cavallaro, Derek Muller (Veritasium), and Xyla Foxlin, you can take advantage of some tricky physics to make this vehicle work. Can you build—or even improve—your own "impossible" wind-powered vehicle for your own science project? Try it and find out!

Summary

Areas of Science
Difficulty
 
Time Required
Short (2-5 days)
Prerequisites
None
Material Availability
Access to a 3D printer required.
Cost
High ($100 - $150)
Safety
The spinning propeller blade can cause injury (as it did in Xyla's video). Science Buddies recommends adding a guard or cage around the propeller blade to reduce the chance of injury.
Credits
Ben Finio, PhD, Science Buddies

Based on "Building the Vehicle Physicists Called Impossible (feat. Veritasium)" by Xyla Foxlin.

Building the Vehicle Physicists Called Impossible (feat. Veritasium)

Objective

Build a working model of an entirely wind-powered vehicle that can travel directly downwind faster than the wind.

Introduction

Watch the following video by YouTuber Derek Muller (Veritasium), which introduces an "impossible" wind-powered vehicle called "Blackbird," built by Rick Cavallaro. Blackbird is powered entirely by the wind—no hidden batteries or other power sources! The vehicle in the video uses some counterintuitive physics. You might expect that the propeller would behave like a wind turbine, which harnesses power from the wind, spinning the wheels to propel the vehicle forward. However, the behavior is actually the opposite: the drag force from the wind on the body of the car pushes it forward, spinning the wheels. The wheels are connected to the propeller with gears and chains, causing it to spin and act like a fan: it blows air backwards and pushes the car forward (due to Newton's third law of motion).

Risking My Life To Settle A Physics Debate

Either way, you might expect it to be impossible for this vehicle to go faster than the wind. Wouldn't that violate the law of conservation of energy? YouTube is full of bogus claims about perpetual motion machines—is this just another hoax? Or, could there be some fundamental errors in the experiment and data collection that just made it seem like Blackbird was traveling faster than the wind? UCLA physics professor Alexander Kusenko thought the latter, and was willing to bet $10,000 that Blackbird's operation was impossible—at least, as Veritasium described it. You can learn about that bet—and the results—in this video:

A Physics Prof Bet Me $10,000 I'm Wrong

Most people do not have the means to build a full-size vehicle like Blackbird, or access to a windy dry lake bed to test it. Thankfully, engineer and YouTuber Xyla Foxlin developed plans for a miniature version of Blackbird that you can build using a 3D printer and parts you can buy online or at a hobby store. You can use her plans to build your own car and demonstrate its operation. Can you devise an experiment to test how changing a variable affects the car's performance using the scientific method? Can you make changes to improve the design using the engineering design process? You won't know until you build one, so try it and find out!

Terms and Concepts

Questions

Bibliography

Materials and Equipment

The following materials are recommended by Xyla Foxlin in the description of her YouTube video. You may also be able to purchase some of the materials at a local hobby shop. Listed quantities are exactly what is required to build one cart, but Xyla recommends purchasing extra parts in case some break, especially ball bearings and plastic gears. You will also need to plan whether you need additional parts for your experiment; for example, you might want to test different gear ratios or different propellers.

Disclaimer: Science Buddies participates in affiliate programs with Home Science Tools, Amazon.com, Carolina Biological, and Jameco Electronics. Proceeds from the affiliate programs help support Science Buddies, a 501(c)(3) public charity, and keep our resources free for everyone. Our top priority is student learning. If you have any comments (positive or negative) related to purchases you've made for science projects from recommendations on our site, please let us know. Write to us at scibuddy@sciencebuddies.org.

Experimental Procedure

  1. This is an open-ended project, so it requires some planning on your part before you get started. The two suggestions here are just that—suggestions. You may choose to follow a different experimental procedure.
    1. For the scientific method:
      1. Choose one thing about the car to change (the independent variable). For example, you could use different propeller diameters or different gear ratios (remember that this means you will need to purchase additional parts beyond what is listed in the materials section).
      2. If you are testing the car outdoors, you can measure the car's speed relative to the wind speed as your dependent variable. Make sure you do many trials in order to account for variation in wind speed.
      3. If you are testing the car indoors on a treadmill, you can measure the car's forward speed on the treadmill as your dependent variable.
    2. For the engineering design process:
      1. Choose something about the car that you want to improve. For example, do you want to make it cheaper to build? Sturdier? Smaller? Make it go straighter so it does not crash? Make it from different materials so it does not require a 3D printer?
      2. Define how you will measure the car's performance. This could be similar to the speed measurements for the scientific method, but it could be something else (e.g. how far or how long the car can drive before crashing), and it might include multiple factors (e.g. speed and cost).
    3. There might be some overlap between the scientific method and engineering design process, and you might wind up using both in your project. For example, if your engineering goal is to make the car faster, it could make sense to use the scientific method to test different variables to see how they affect the car's speed.
  2. Build your car by following the instructions in Xyla Foxlin's video. Science Buddies recommends adding a protective guard around the propeller to prevent accidental cuts, especially when operating the car on a treadmill. Depending on your exact procedure, you might need to make sure it is easy to swap out parts (e.g. propellers) on your car, or build more than one car to test.
  3. Building the Vehicle Physicists Called Impossible (feat. Veritasium)
  4. Follow either the scientific method or the engineering design process to test and/or improve your car.
  5. Communicate your results! Did you determine how a certain variable affects the speed of the car, or were you able to make improvements to Xyla's design? Make sure you are prepared to explain how the car works, as you might run into people who claim your car must be a hoax and is "impossible" (e.g. it must have a hidden battery somewhere).
icon scientific method

Ask an Expert

Do you have specific questions about your science project? Our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Variations

  • Can you build a car that is a more exact replica of the Blackbird vehicle (with the propeller perpendicular to the ground) using gears and a chain?
  • Can you build a larger (or smaller) version of the car?

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General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Finio, Ben. "Build an 'Impossible' Wind-Powered Car." Science Buddies, 20 July 2021, https://www.sciencebuddies.org/science-fair-projects/project-ideas/ApMech_p056/mechanical-engineering/impossible-wind-powered-car. Accessed 24 June 2022.

APA Style

Finio, B. (2021, July 20). Build an 'Impossible' Wind-Powered Car. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/ApMech_p056/mechanical-engineering/impossible-wind-powered-car


Last edit date: 2021-07-20
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