Dextrorotatory and dextrorotation are terms used in chemistry to describe the direction in which a substance rotates plane-polarized light. When a substance is said to be dextrorotatory, it means that it rotates plane-polarized light to the right or clockwise direction, whereas when it is levorotatory, it rotates plane-polarized light to the left or counterclockwise direction.
The terms "dextrorotatory" and "levorotatory" come from the Latin words "dexter" meaning "right" and "lævus" meaning...
In the air, there's nothing holding the body of the helicopter still - so the rotor blades spin one direction, but the torque applied to spin the rotors tries to spin the body of the helicopter in the opposite direction. The little rotor on the tail helps keep the body of the helicopter pointed in the same direction.
Balance on a bicycle is a matter of constantly correcting against falls, and it's easier when the speed is higher because the inertia of moving forward overcomes the need for corrective actions.
