Here, we have to find out the position of the bubble in the spirit level. Now a spirit level is given below.
A spirit level consists of a glass tube closed at both the ends containing a liquid with an air bubble. The air bubble can move inside the tube. When the air bubble is at the centre, the spirit level is horizontal.
When the spirit level is rotated about axis through one end; the air bubble will come to the inner edge of the container. When a system of particles is subjected to rotational motion, the heavier ones will settle at the outer edge of the tube and lighter ones at the inner edge. This principle is used in centrifuge. That is, Since the air bubble is lighter than the liquid, it will come to the inner edge of the container.