Page:Popular Astronomy - Airy - 1881.djvu/121

Rh would carry it in a second of time to B, and if gravity were so strong that in one second the body would fall from rest to C, then the ball would describe the curve AD; but if gravity were so much increased that a ball would fall from rest to C' in one second of time, then the ball would describe the curve AD', which is more curved than AD. In the next place, if two balls are projected with different velocities, without any alteration in the force of gravity, the path of that ball which is projected with the smaller velocity will be more curved. Thus, in Figure 35, if the force of gravity were such as



would make a ball fall from rest to C in one second, and if two balls are projected, one with a smaller velocity which would carry it to B in one second, and the other with a greater velocity which would carry it to B' in one second, then the former ball (or that projected with the smaller velocity) will reach D in one second, describing a very curved path AD; while the latter (or that projected with the greater velocity) will reach D', describing the path AD', which is much more nearly straight than AD. Everybody knows the motion of a stone thrown from the hand; its path is much curved, and it reaches the ground before it has gone far. But if you watch the motion of a cannon ball, which you may do if you stand