Becuase it does not have a reverse gear; reverse gear in a gearbox requires more cogs and drives so it makes the gear box alot more heavier than it needs to be. A bike is meant to be moveable by 'hands & feet'. In the early days (and in some military applications) some combinations (motorcycle & side car) did have a reverse gear; the old German BMW combo also had a drive shaft to the third wheel under the side car.
Redhound, BloodPost, Dirn
it is Red hound, blood post , and dirn
Look it The shearing action/force which takes place in y-direction(transverse dirn.)is known as transverse shear...........
When AC flows through a conductor, charges continuously alternate their direction of movement back and forth along the conductor. This causes them to oscillate in a periodic manner. The direction of current flow changes with the alternation of the AC signal, resulting in the back and forth motion of charges.