The Vibration of Rods and Tubes
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
p-226
2025-11-19
27
A rod fixed at one end may be put in transverse vibration by being struck or plucked at the free end - as in the music box. The longer the rod, the lower the tone produced.
Rods may be made to vibrate longitudinally as well as transversely.
Demonstrations. - Hold a glass rod, a meter long or more, by the middle with one hand, while with the other you draw a moist cloth lightly from the middle to the end. The rod will be thrown into longitudinal vibrations, and the fundamental tone will be produced. Do the same with a wooden rod, a brass rod, and a brass tube of the same length and diameter, using a rosined cloth for a rubber. Does the pitch of the tone depend upon the material of the rod?
Repeat the above demonstration with two glass tubes of different diameters, but of the same length. Does the pitch of the tone depend upon the diameter of the tube? Repeat with one of these tubes and another of the same diameter but only half as long. Does the pitch depend on the length of the tube? How do the two tones compare?
The sound caused by rubbing the tubes and rods in the above demonstrations is due to longitudinal vibrations. That such vibrations exist may be shown as follows:
Demonstration. - Clamp a brass rod firmly to a block upon a table as shown in Fig. 2. Suspend an elastic ball so that it will rest against one end of the rod, and then draw a rosined cloth from the middle to the other end.
The longitudinal vibrations will cause the rod to give out a high tone, and will repel the ball from the end of the rod.
The mechanical effect of vibrations in tubes is sometimes very great. It is not uncommon for a test tube to be cracked into a spiral ribbon running from end to end, on being wiped with a damp towel. If a glass bell jar is bowed vigorously a few times with a violin bow, it may be shattered even if the walls are a quarter of an inch thick.
الاكثر قراءة في الميكانيك
اخر الاخبار
اخبار العتبة العباسية المقدسة
