We often hear that objects appear to be weightless in a spaceship circling round the Earth. In order to examine the effect in some detail, let us first define, what do we mean by the weight? The real weight of an object is the gravitational pull of the Earth on the object.
If, however, a satellite in a circular orbit is at an appreciable distance h above the Earth’s surface, we must take into account the experimental fact that the gravitational acceleration decreases inversely as the square of the distance from the centre of the Earth (Fig. 5.16).
The body is metamerically segmented. The body becomes divided transversely into a number of similar parts or segments. The subdivisions may be indicated externally by constrictions of the body surface.
The name nematode means “pointed ends”. The animals included in this group have elongated worm like body with pointed ends. The nematodes are triploblastic and pseudocoelomates. One end of the body is anterior, however the head is not clearly marked and there are no special sense organs at this end