Fig. 32.—BATTLEDORE AND SHUTTLECOCK.
837. Why do we hear a noise when we strike the shuttlecock with the battledore?
Because the percussion of the shuttlecock upon the parchment of the battledore causes it to vibrate, and the vibrations are imparted to the air.
838. Why is the sound a dull and short one?
Because the vibrations of the parchment are not very rapid, therefore there is little intensity in the vibrations of the air.
839. Why does the exercise, afforded by playing battledore and shuttlecock, make us feel warm?
Because it makes us breathe more freely, and causes the blood to flow faster; we, therefore, inhale more oxygen, which produces heat by combining with the carbon of our blood.
840. Why does a kite rise in the air?
A kite rises in the air by the force of the wind, which strikes obliquely upon its under surface. The string is attached to the "belly-band" in such a manner that it is nearer the top than the bottom of the band: this causes the bottom of the kite, when its surface is met by the wind, to recede in the direction of the wind: the top is accordingly thrown forward, and the kite is made to lie obliquely upon the current of air moving against it. The kite then being drawn by the string in one direction, and pressed by the air in another direction, moves in a line which describes a medium between the two forces acting upon it.