I needle of a record player moves 7.2 cms when playing a particular record. If the record makes 900 revolutions, find the width of the groove?

Total distance covered by a needle in playing a particular record = 7.2 cms
Number of revolutions = 900
So, width of the groove = $\frac{7.2}{900-1}=\frac{7.2}{899}$ = 0.00801 cm

[100 centimeter (cm) = 10,00,000 micrometer (um)

1 cm = 10000 um

0.00801 cm = 80.1 um]