Why is it effortless to balance a moving bike,but almost impossible to do so when

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SartajBcvs

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it's dead stationary? ? Without putting your feet on the floor that is.
What's the physics involved.
Detailed explaination please.
Thanks in advance.
 
Let the c.g of the bike be at height h from the ground.
If the bike is at rest (v = 0), for a small angle of inclination of the bike from the vertical (say to the left), the vertical component of the normal reaction balances the weight of the bike. (It is because of the fact that the bike does not go into the ground) The horizontal component of the normal reaction pulls the bike toward the left and in fact it gives torque about the point of contact. It rotates the bike leftwards, for us who are viewing the cycle. The cycle rotates in a vertical plane and falls down.

If the bike were not at rest but moves with certain velocity, the same left wise force now acts as the centripetal force and makes the bike to move along a circular path of radius r.
The bike moves along a circle in horizontal plane.( compare this with the previous case)


The one who drives the bike feels this circular horizontal motion rather than the falling down along a vertical circle the feeling which was when the bike was at rest. With no time he adjusts his balance and moves in his path unless he wants to go in the circular path.
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