862. Why does the hoop, in falling, make several side revolutions?
Because its onward movement, not being quite expended, influences the centre of gravity of the hoop, and changes its line of direction. The hoop is also elastic, and when its sides strike the earth, they spring up again, and continue turning until the opposing forces are overcome by the attraction of gravitation.
863. Why will a little boy balance a large boy on a see-saw?
Because the "see-saw" may be placed so that its ends are at unequal distances from the centre. This gives the little boy the power of leverage, by which is meant the increase of power, or weight, by mechanical means.
Fig. 44.—BOYS AND "SEE-SAW."
864. Why does the little boy sink to the ground when the larger boy slightly kicks the earth?
Because the larger boy, by kicking against the earth, opposes by mechanical force the attraction of gravitation acting upon him, and he becomes temporarily less attracted to the earth than the little boy.