handspinner - DIY kit for Students

In the kit, there are two disks with holes. These are the spinners, which produce hissing sound as you spin them rapidly. Let us do this first. Take one disk and make a loop of thread given in the kit whhile passing the thread through t wo small holes in the centre of the disk. The loop should be of optimum length, so take thread of approximately 100 cm. length. Spin the

spinner rapidly as shown in the figure. Once it gets enough spin, it starts producing hissing or whistling sound. You may repeat this experiment with another disk. It will also produce similar sound. Keen observation will reveeal that there is some difference in the sound produced by two disks. Let us knnow the science behind spinners.

How does it happen ?

Let us first know, what is 'Sound'? Sound is a form of energy produced by something vibrating. Or we can say that vibrating energy is converted into sound energy. Sometimes we can see these vibrations, while most of the times we cannot. If we pluck a tightly held elastic band, it shows vibrations, while it produces sound. However, when we speak, sound is heard but vibrations are not seen. When we speak, we set air molecules around us vibrating. Air acts as a medium and carries these vibrations or sound waves to our ears. Look at the disks that you are spinning. They have a few holes near their periphery. As we spin them rapidly, air passes through these holes and vibrations are set in. These vibrations produce sound which is audible to human ears. Even when we spin the disks slow , vibrations are created, but sound produced by these vibrations is not audible to human ears. If we notice carefully, the disk with small holes produces sound with higher pitch. You must know that the technique of producing sound by passing air through holes is used in factory sirens.