A quantitative yo-yo is constructed with a disk fixed to an axle and it has string wrapped around it. The radius of the disk is 5 mm. When the disk is dropped it revolves about a perpendicular line through the center as axis. In this process string is unwrapped with each rotation. The length of string unwrapped wit one revolution is equal to the circumference of the disk.
Here, the circumference of the disk is equal to `2*(5/1000)*pi` m. As the disk falls down through a vertical distance 30 cm, the number of revolutions of the disk is equal to `(30/100)/(2*(5/1000)*pi)`
The disk has revolved approximately 96 times in the vertical drop of 30 cm.