Why it is easy to balance a running bicycle as compared to a stationery one?
When the wheels of the bicycle are turning, they possess an effect called gyroscopic effect. That is, a body rotating around itself tends to keep its axis of rotation unchanged. So a bicycle wheel when it is turning, tends to maintain its vertical stance. The faster it turns the greater the gyroscopic effect. A heavier wheel also has more of that effect. A bigger wheel has more of this effect too. The front wheel of the cycle also is held at an angle to the horizontal. This is called Caster angle. If the angle is more towards vertical, the easier it is to steer the vehicle. The more horizontal the angle is, the more stable the wheel is. A properly chosen caster angle gives stability to the cycle while still maintaining some ease of steering. The stability of a moving bicycle is dependent upon the gyroscopic effect of the wheels and the stability offered by the caster angle of the front wheel. Hope I helped.
