How can you make a really loud sound with a ruler?

Answer 1

A ruler has a flat, wide and long surface, more than 1 inch wide and sometimes 12 inches long, it has 12 square inches in area.

When you hold the ruler horizontally and suddenly stomp it flat over a desk, the strong loud sound happens.

During the time you are moving and accelerating the ruller towards the desk, you are compressing air under the bottom part of the ruller. The speed and mass of the ruller hit the desk fast, really fast, it may reach more than 20km/h.

Within 1/4 of an inch from the desk, the ruler is compressing air against the desk, this air has no way to go, except to the sides.

6 cubic inches of air being moved to the sides at 20km/h in a sudden direction change, creates a loud noise, mostly because the vacuum created over the ruler, suddenly occupied by air that is surrounding the ruler.

Air compression and decompression causes lots of noises and sounds we hear all day long. Clapping is one of them. Three people clapping can block any other people conversation, it is really loud.

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