The Vibration of Plates
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
p-230
2025-11-23
12
If a thin plate of metal or glass is clamped to a support at the middle, and a bow is drawn across its edge, it will be thrown into vibration
and will produce sound. The positions of the nodal lines of the plate can be shown very readily as follows:
Demonstrations. - Sift sand evenly over the surface of a brass plate fastened by the middle, as the first one in Fig. 1. Place a finger at one corner and draw a bow across the middle of one side. The sand will be thrown violently about, and will finally come to rest on those parts of the plate that do not vibrate, so that the lines of sand indicate the nodal lines. Figure 1 shows a number of plates differing in form, size, and thickness, and a few of the many interesting figures that can be produced by them. If the plates are clamped by the corner or at one side, a new set of figures will be obtained.
Scatter a little lycopodium powder on the plate with the sand, and it will be found, on vibrating the plate, that the powder will collect over the places of greatest vibration instead of at the nodal lines as the sand does. Examine carefully and explain why this happens.
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