the fun side of mechanics day three countersteering
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The Fun Side of Mechanics: Day Three! Countersteering

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The Fun Side of Mechanics: Day Three! Countersteering. By Jonathan Abbott. Quick Review. Newton’s First Law Net Force Newton’s Second Law Friction Kinetic vs. Static Newton’s Third Law Center of Mass. Today: Countersteering.

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Presentation Transcript
quick review
Quick Review
  • Newton’s First Law
  • Net Force
  • Newton’s Second Law
  • Friction Kinetic vs. Static
  • Newton’s Third Law
  • Center of Mass
today countersteering
Today: Countersteering
  • Countersteering is when you shift your point of contact (with the ground) in the opposite direction to help you move.
  • So in order to balance, you change where you touch the ground.

Too much this way, ahhh!

Too much that way, ahhh!

Points of Contact

simon says
Simon Says

We are going to practice how we balance.

two ways to balance
Two ways to balance



Twist body

Change Point of Contact

Change Shape of


What we are talking about today

What we will discuss later

first safety
First Safety!
  • The contact force between you and the ground can hurt!
  • Helmet
    • Wear it, love it, and it will love you back!
idling on a unicycle overcompensating
Idling on a Unicycle: Overcompensating

Move the

point of contact more than the center of mass

what is the physics of idling
What is the physics of Idling?

Think about the net force

what about the pogo
What about the Pogo?
  • When up in the air, twist your body so that the point of contact underneath you changes, allowing you to remain upright.
  • Overcompensate!
a rolla bolla
A Rolla Bolla
  • It’s simple a board on top of a rod thing; like a plane on a cylinder. Let’s draw a force diagram (see next slide)
What forces are between the board and cylinder?
  • What forces are between the ground and the cylinder?

Let’s identify the forces in a force diagram.

rolla bolla analysis
Rolla Bolla Analysis
  • So how does one balance?
  • By changing the angle of the board on the plane, there becomes frictional forces between the board and cylinder and the cylinder and the ground that together push the person to the left or right.
  • To balance, one has to overcompensate to stay upright.
parents how smart are they
Parents – How smart are they?
  • When you were first learning to ride a bicycle, what advice did your parents give you?
  • Okay, so using what we have talked about today, how might I be able to make a left turn on a unicycle?
the trick is countersteering
The trick is countersteering
  • I have to turn to the right to make a left turn!
  • This way I can lean.


Turn right to lean

Turn left

sharp turning on a unicycle
Sharp turning on a unicycle
  • This makes it a little easier to see.
  • I have to turn right to go left.
  • For a motorcyclist or bicyclist to turn left, they will have to first swerve to the right in what is known as countersteering.
  • They will need extra space!

b ikes and scooters
Bikes and Scooters!
  • You do this on a bike, but it can be hard to see.
  • If you ride slowly, you may notice it more.
a little harder to unicycle
A little harder to Unicycle
  • Unicycles can also fall forward or backward.
  • So, if leaning too far forward, speed up temporarily to get the unicycle in front and then slow down..
  • If leaning too far backward, slow down until upright, and then continue forward.
  • It’s like “idling” while moving forward.