Question

why do we need three semi circular canals in each ear rather than only one?

Answer 1

The semicircular canals of the inner ear are sensory organs that provide the brain with information about head movement and position. They are filled with fluid that moves due to inertia when the head moves, triggering nerve endings. There are three so that movement can be sensed in all three
spatial axes. You can turn your head, tilt it
forward and backward, and side to side. Yaw, pitch, and roll, as with an airplane. Any one of these motions causes the fluid in one of the canals to move. If you spin around rapidly and suddenly stop you become dizzy because the fluid in your canals moves more rapidly than it usually does.