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取一根长约35—40cm的细玻管,用线系住平衡点挂在铁架的铁圈或铁夹上,再把事先糊好的空纸袋挂在玻管的两端,并使之平衡后,
Take a thin glass tube about 35-40cm in length, and tie the balance point on the iron ring or iron clip of the iron frame, and then hang the preliminarily empty paper bag on both ends of the glass tube and make it After balancing,