The outer rail is made higher than the inner rail, so as to overcome the tendency of the cars to run off the track.
What grand example have we of the action of these two forces?
The earth and other planets that move around the sun, are kept in their places by the action of these two forces.
When a ball strikes a solid body and bounds back, what is that motion called?
It is called reflected motion.
At what angle does the ball leave the solid body?
It bounds off from the solid body, so that the angle of reflection is always equal to the angle of incidence, as is shown in [Fig. 39].
Fig. 39.
How may a stone be skipped on a smooth pond?