Take a plastic or tin can or a plastic glass. Remove its bottom. Stretch a piece of rubber balloon across one end and fix it with a rubber band. Put a few grains of say ragi or bajra on the stretched rubber. Now ask your friend to shout 'Hoorrey..... Hoorrey.....' from the open end of the glass. Observe the dancing of the grains up and down. Discuss the reason behind this.
(Explain the reason in brief)​