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# Physics/mechanics

Question
Sir, it is easy for us to balance  a bicycle when we are going fast , but it becomes  more difficult when we go slower.! Why this happens?

Hello Vikram,

For a webpage with a good discussion of bicycle dynamics, go to
http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics
In particular, see the section titled Balance and the one below it titled Forward speed. I had generally heard that the relationship between increasing speed and increase of ease in balancing was due to the gyroscopic properties of the rotating front wheel. The gyroscopic properties would increase with increasing speed. This site says that those properties contribute, but steering and trail also contribute. The rider is generally responsible for the use of steering in maintaining balance. See the first paragraph in the Balance section. Positive trail makes the steering input more effective in balance control.

Here is my summary of how speed aids the effectiveness of the steering input. When riding straight, the bike is balanced when the center of mass is above an imaginary line drawn between the contact patch of the 2 tires. In a tip, the center of mass moves to the left or right. To correct a tip, the rider steers to move the tires so that the line between the tire contact patches is again below the center of mass. The faster the bike is going, the more quickly the tires move to the left or right for a given steering angle.

I hope this helps,
Steve

Physics

Volunteer

#### Steve Johnson

##### Expertise

I would be delighted to help with questions up through the first year of college Physics. Particularly Electricity, Electronics and Newtonian Mechanics (motion, acceleration etc.). I decline questions on relativity and Atomic Physics. I also could discuss the Space Shuttle and space flight in general.

##### Experience

I have a BS in Physics and an MS in Electrical Engineering. I am retired now. My professional career was in Electrical Engineering with considerable time spent working with accelerometers, gyroscopes and flight dynamics (Physics related topics) while working on the Space Shuttle. I gave formal classroom lessons to technical co-workers periodically over a several year period.

Education/Credentials
BS Physics, North Dakota State University
MS Electrical Engineering, North Dakota State University