How to Win a Bike Race: Using Gears
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How to Win a Bike Race: Using Gears

October 26, 2019


Gears are everywhere, in
cars, elevators, even bikes. None of these objects
would work as well as they do without the use of gears. But how can we
understand what gears do? We’re going to take
a close look at gear and try and understand a
little more the physics and engineering that
makes them work. Then we’ll use what we’ve
learned to try and understand how to win a bike race. When you’re getting
ready for a bike race, the most important thing
to know about is torque. A torque is made up of
a force and a distance. A force is a push or
a pull, and that force is applied at a certain
distance away from something that we’ll call the pivot point. Watch as I try to push
this revolving door. It’s hard here, but
much easier here. Why is that? Well, when you’re
trying to push the door close to the pivot point,
you need a big force. As you move away
from the pivot point, you increase the distance
component of the torque. And then you have
to apply less force. But what’s the trade off? Let’s take a look at a top view. This revolving door needs a
certain torque to spin around. You can get that
torque by applying a big force at a
small distance away from the pivot point, or a
small force at a big distance. However, if you
apply a large force, you only need to travel around
a small circle to rotate once. Smaller force is
easier, but you need to travel in a bigger circle. Gears work in a similar way. Gears touch each other,
and therefore, apply a force to each other. And the size of the gear is
what determines the distance part of the torque. One torque can drive
the first gear, and you get a different
torque out of the second gear, in this case a bigger one. The trade off? The bigger gear
provides a bigger torque but has to travel
a longer distance before it spins around once. Sound familiar? Bikes use something
called a sprocket, which is essentially a special
gear for use with a chain. For now, let’s just
say we can only change the size of the
back sprocket, the one that drives the back wheel. But how will changing the
sprocket size or shifting gears help you to be a better biker? So to test this out, we’re
going to have a race. In this race the
first cyclist, me, is going to be stuck
using a big sprocket. Second cyclist is going to
be stuck using smaller one. [MUSIC PLAYING] And they’re off. It looks like cyclist two
is off to an early lead, with cyclist one pedaling
furiously to keep up. Oh, and it looks like cyclist
two can’t get enough torque to get up that hill. Cyclist one breezes past her. Can cyclist two catch
up on the downhill? And she does it. It’s going to be a close finish. And cyclist two wins. As you could see, using
the larger sprocket let me put a huge
torque on the wheel, making the hill a piece of cake. But to get anywhere, I
had to pedal my legs off. Just like moving the revolving
door far from the pivot point, it’s easier. But there is more
distance involved. The smaller sprocket lets
cyclist two turn the wheel around many times, but
without the extra torque, she had trouble
getting up that hill. Just like moving the door
close to the pivot point, it’s harder, but less
distance is involved. I hope you learned a little
something about gears and the trade offs involved. There is still
plenty more to learn. See you next time. [MUSIC PLAYING]

Only registered users can comment.

  1. I appreciate the excellent uses of story telling, first rate graphics and clever video editing. These enhanced the ways to follow and understand the lesson as it unfolded.

  2. PLEASE make many more educational videos during the coming years. You have a masterful touch with this new media. There will be learners that quickly understand lessons, easily recall them and make suitable applications.

  3. Hi John, we will be releasing two videos per week (we try for Tuesdays and Thursdays) throughout this semester and maybe into the summer if we get enough made. Keep coming back and let us know what you all think and like 🙂

    Thanks, MIT+K12

  4. so.. just improve my legs power so i can use and stuck on the biggest gear to climb and sprint ne ahahahhaah

  5. Hey guys ! thanks for the awesome video ! I have a question tho .. you taught us the use of back wheel gear .. But what does the front wheel gear do ?

  6. What a waste of time making this video, the bikes were completely different which means there were more variables than the gear size.

    Winning a race comes down to fitness, tactics,and skills on the bike.

    gear selection is something that is made using rider preference generally guided by variables such as wind,gradient, terrain, etc

    and an easy check is cadence for optimum power/economy of effort on the flat your cadence should be around 90rpm

    I can guarantee no one will win a race using only the information gleaned from this clip.

  7. Yоur соursе doеееsn't work at me tооо gеt Bikеееe Rаcе Frее, nеverthеlеss i found а greatеr оnе toоl. https://twitter.com/d98523e9fd12f49ed/status/779266899116892164?ZxJr=52054655-a3f5-48fb-b6d1-0b51aed595ee Hоw tо Win а Bike Rаace: Using Gеаrs

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