For a couple of minutes of paper or paperboard will be able to make strenuously device that will instantly show you the centre of any circle, for example, the base of the cylinder. The secret lies in the fact that the rays arrows, encircling a circle located at an angle of 90° to each other, and a “shaft” of the arrow divides this angle in half, and it always passes through the center.
Recommend to read
THE FLIGHT ACROSS THE ENGLISH CHANNEL WITHOUT A MOTOR
To fly like a bird, the strength of your muscles, very tempting; dreamed about it many of our ancestors. Already in the XV century, when on flights in the modern sense could not even...
THE TIMER CONTROLS THE SOUND
The device, whose scheme is published in the journal "Popular electronics" (USA), produces a positive pulse when a sound (for example, firing of the gun) reaches the microphone B1 (see...
