The Problem
You all must have seen that chalks make a squealing sound when teachers use them to write on the black boards. It is an usual phenomenon which as a student and, now, a teacher I have always hated. Can this be corrected? Read on to find out.
The Answer
As a teacher when I hold the chalk in a wrong position or orientation with the board the chalk tends to stick to the board. Then when I try to push it forward to write on the board the chalk "slips" on the board and vibrates along it. While vibrating it hits the board several times per second creating the squealing sound. As the chalk moves faster the squeal tends to die down and the chalk starts to "stick" back on to the board preparing for the next round of squealing.
Better quality non-dust chalks can reduce the squealing considerably.
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