A group of teens riding bicycles. Image © FatCamera, iStockphoto.com

A group of teens riding bicycles. Image © FatCamera, iStockphoto.com

STEM in Context

How Can Understanding Physics Help Me Go Faster on My Bike?

Kaitlyn Bailey

Summary

You don’t have to pedal harder to go faster. You just have to understand a little bit about dynamics, gravitational force and friction!

Do you or does someone you know ride a bike? Chances are you’ve answered yes. Today, people all around the world use bikes every day for transportation, for exercise, and even just for fun. But this wasn’t always the case. The first bicycle was invented in 1817. Before that, most people believed it would be impossible to balance on top of two thin wheels, one in front of the other.

Early bicycle known as a Laufmaschine, which means “running machine.” This one was built around 1820
Early bicycle known as a Laufmaschine, which means “running machine.” This one was built around 1820 (Source: Gun Powder Ma [CC BY-SA 3.0] via Wikimedia Commons).

 

Did you know?

In the early days of the bike, people had to take special bike-riding classes. This is similar to how you have to take driving lessons before you can get your driver’s license today. 

If you’re taking a leisurely bike ride into town to get an ice cream cone, you might not care how fast you’re going. But what if there was a delicious holiday meal waiting for you at home? I bet you’d want to go fast then!

When you think of going faster on a bicycle, you probably imagine working harder. Would you believe me if I told you that there are ways to increase your speed without using any more effort? Well, there are!

Let’s look at some of the forces that oppose the forward motion of a bicycle. And then, let’s look at some ways that you can decrease the magnitude of these forces so that you can go faster.

How does gravity affect you on your bike? 

Why is it harder to cycle up a hill than on flat ground? Because when you are biking up a hill, gravity is pulling you backwards down the hill. Gravity is the force that prevents us from floating away to outer space. The heavier you are, the greater the force of gravity acting on you. That is because your weight is your mass multiplied by the force of gravity (9.8 Newtons/kg). In other words, you can decrease the force of gravity pulling on you by making you or your bicycle lighter. For example, you can ride a bike with a lower mass. You could also carry a lighter backpack. Or maybe leave your rock collection at home if you are planning to bike up a hill!

Did you know?

Carbon fibre is one of the lightest materials used to make bike frames. A carbon fibre bike can have a weight of less than 6.8 kg (15 lbs.). That’s about the same weight as a small dog like a Toy Spaniel!

How does air resistance affect you on your bike? 

When you are biking, air resistance can seriously slow you down! Air is made up of particles, and you have to push them aside as you move forward. It’s kind of like being a football player and having to push opposing players out of your way as you run across the field.

Air resistance (also known as drag) is most noticeable when you are travelling quickly. You might not notice it when you are walking, but you can probably feel it if you hold your arm out the window of a moving car.

To increase your speed on a bike, make your body smaller, or more aerodynamic, so there are fewer air particles that need to be pushed aside. This is why cyclists in races often hunch down low over top of their handlebars.

Canadian racing cyclist Alex Cataford
Canadian racing cyclist Alex Cataford (Source: Canadian Cyclist [CC BY-SA 1.0] via Wikimedia Commons).
A bicycle tire that is getting flat
A bicycle tire that is getting flat (Source: Alexas_Fotos via Pixabay).

How does rolling resistance affect you on your bike? 

Have you ever had to push a heavy object, such as a desk, across the carpet? It’s a lot of work, isn’t it? This is because there are electromagnetic forces attracting the molecules in the desk to the molecules in the ground. If you want to move the desk, you have to first overcome these forces. We call this type of resistance sliding friction. What if you added wheels to the bottom of that desk? Moving it would be easier, of course! That’s because wheels don’t have to overcome sliding friction. But there is a different, smaller force that wheels have to overcome. It’s called rolling resistance.

Want to see how rolling resistance slows you down? Watch the tires of someone else’s bike as they ride. If you look really closely, you will see that the tires partially flatten. When this happens, some of the kinetic energy (the work your legs are doing when they’re pedaling) is lost. This means you will move more slowly.

 

How can you decrease rolling resistance? Pump your tires with more air! Your bike's tires are filled with air. Higher air pressure makes them firmer - that is, they don't flatten as much, which means there is less of the tire in contact with the ground. For example, road bikes are made to go fast, and they typically have the highest air pressure in their tires. The less your tires flatten, the smaller rolling resistance you'll face, and the faster you'll go! 

To sum up...

Learning about forces is just like riding a bike. Once you get the hang of it, it’s easy! So the next time you’ve got a holiday dinner waiting for you and you’re racing the clock on your bike to get home, what should you do? First, take a minute to empty your backpack of anything heavy. Then, pump up your tires. Finally, while you are riding, crouch down low over your handlebars. These tips and tricks will ensure you don’t miss a bite!

Did you know?

Recumbent bicycles (the ones that look like the rider is lying on their back) are more aerodynamic and have less air resistance than a regular bicycle. That’s why the Union Cycliste Internationale has banned these types of bikes from world speed record competitions. Their shape gives them too much of an advantage!

Starting Points

Connecting and Relating
  • Where or when have you experienced air resistance? 
  • What activities have you done that involve sliding friction in some way? 
Connecting and Relating
  • Where or when have you experienced air resistance? 
  • What activities have you done that involve sliding friction in some way? 
Relating Science and Technology to Society and the Environment
  • What is the economic benefit to reducing or increasing the strength of certain forces acting on a bicycle?  Consider different parts of a bicycle and the forces at work (e.g., body, tires, brakes, gears, etc.).
  • How are science and technology integral to competitive cycling?
Relating Science and Technology to Society and the Environment
  • What is the economic benefit to reducing or increasing the strength of certain forces acting on a bicycle?  Consider different parts of a bicycle and the forces at work (e.g., body, tires, brakes, gears, etc.).
  • How are science and technology integral to competitive cycling?
Exploring Concepts
  • What is the difference between sliding friction and rolling friction? 
  • Draw a picture of a bicycle  in motion and identify the forces mentioned in the article that are acting on the bike. Use arrows to indicate which direction each force is acting. 
  • What is the relationship between air resistance and speed? In sport cycling how is the force of air resistance manipulated to increase a competitors chances at winning a race? Consider both short distance sprinting and long distance racing in your answer.
Exploring Concepts
  • What is the difference between sliding friction and rolling friction? 
  • Draw a picture of a bicycle  in motion and identify the forces mentioned in the article that are acting on the bike. Use arrows to indicate which direction each force is acting. 
  • What is the relationship between air resistance and speed? In sport cycling how is the force of air resistance manipulated to increase a competitors chances at winning a race? Consider both short distance sprinting and long distance racing in your answer.
Nature of Science/Nature of Technology
  • How are newly designed vehicles tested for safety? Why is this step part of the Technological Problem Solving process (or the Design & Build process)?
Nature of Science/Nature of Technology
  • How are newly designed vehicles tested for safety? Why is this step part of the Technological Problem Solving process (or the Design & Build process)?
Media Literacy
  • Have you heard about carbon fibre bicycles in the media? In what context is carbon fibre mentioned? What features and benefits of carbon fibre are discussed or described?
Media Literacy
  • Have you heard about carbon fibre bicycles in the media? In what context is carbon fibre mentioned? What features and benefits of carbon fibre are discussed or described?
Teaching Suggestions
  • This article can be used for senior physics for teaching and learning related to dynamics, gravitational force and friction. Concepts introduced include forces, gravity, weight, mass, air resistance, rolling resistance, sliding friction, kinetic energy and air pressure. 
  • After reading the article and viewing the embedded video, teachers could have students complete a Concept Definition Web Learning strategy for one of the key concepts introduced in the reading, such as friction or air resistance. Ready-to-use Concept Definition Web reproducibles are available to download in [Google doc] and [PDF] formats.
  • Teachers could also have students compare and contrast rolling friction with sliding friction, using a Venn diagram learning strategy. 
  • For a mathematics skills connection, teachers could have students calculate their weight in Newtons on the moon, low Earth orbit (as on the ISS) and on different planets in the Solar System. Students could be provided with the acceleration due to gravity measurements for each solar body or students could conduct research to find these measurements and then make the weight calculations. For example:
    • Acceleration due to gravity: 
      • On the ISS or in Low Earth Orbit (LEO)  =  9 m/s2 
      • Surface of the Moon = 1.625 m/s2
      • Surface of Mars = 3.711m/s2
Teaching Suggestions
  • This article can be used for senior physics for teaching and learning related to dynamics, gravitational force and friction. Concepts introduced include forces, gravity, weight, mass, air resistance, rolling resistance, sliding friction, kinetic energy and air pressure. 
  • After reading the article and viewing the embedded video, teachers could have students complete a Concept Definition Web Learning strategy for one of the key concepts introduced in the reading, such as friction or air resistance. Ready-to-use Concept Definition Web reproducibles are available to download in [Google doc] and [PDF] formats.
  • Teachers could also have students compare and contrast rolling friction with sliding friction, using a Venn diagram learning strategy. 
  • For a mathematics skills connection, teachers could have students calculate their weight in Newtons on the moon, low Earth orbit (as on the ISS) and on different planets in the Solar System. Students could be provided with the acceleration due to gravity measurements for each solar body or students could conduct research to find these measurements and then make the weight calculations. For example:
    • Acceleration due to gravity: 
      • On the ISS or in Low Earth Orbit (LEO)  =  9 m/s2 
      • Surface of the Moon = 1.625 m/s2
      • Surface of Mars = 3.711m/s2

Learn more

How to cycle faster for free - Ride your bike faster with less effort (2013)

Video (3:22 min.) from the Global Cycling Network giving tips and tricks on how to go faster, and save effort.

Bicycle science (2017)

Article from ExplainThatStuff that explains the science behind bicycles.

Friction (2016)

Video (10:58 min.) from Crash Course Physics giving information about what friction is, different kinds of friction, and how it impacts the world.

References

Canada 2067. (2017, May 12). Science of cycling.

Connolly, J. (2016). Understanding the magic of the bicycle. Morgan & Claypool Publishers.

Gross, A., Kyle, C., & Malewicki, D. (1983). The aerodynamics of human-powered land vehicles. Scientific American, 249(6), 142-152. DOI: 10.1038/scientificamerican1283-142

Penn, R. (2011). It's all about the bike: The pursuit of happiness on two wheels. London: Penguin Books Ltd.

Persson, B. (2013). Sliding friction (2nd ed.). Springer, Berlin.