The Fun Side of Mechanics: Day Three! Countersteering

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# The Fun Side of Mechanics: Day Three! Countersteering - PowerPoint PPT Presentation

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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### 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
• 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

We are going to practice how we balance.

Two ways to balance

Countersteering

Continuum

Twist body

Change Point of Contact

Change Shape of

Body

What we are talking about today

What we will discuss later

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

Move the

point of contact more than the center of mass

What is the physics of Idling?

• 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
• 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
• 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?
• 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
• I have to turn to the right to make a left turn!
• This way I can lean.

Normal

Turn right to lean

Turn left

Sharp turning on a unicycle
• This makes it a little easier to see.
• I have to turn right to go left.
Beware!
• 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!

http://www.flickr.com/photos/jduty/5016023830/sizes/m/in/photostream/

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
• 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.