Question

a hallow circular device containing small metal balls​

Answer 1

Answer:

ball bearings

Ball-bearing is a hollow, circular device containing small metal balls. It is fitted around the moving part of Machines, search as an axle. The ball-bearing reduces friction by converting sliding friction into rolling friction therefore ball bearings are used in machines.

Answer 2

Answer:

ball bearings

Ball-bearing is a hollow, circular device containing small metal balls. It is fitted around the moving part of Machines, search as an axle. The ball-bearing reduces friction by converting sliding friction into rolling friction therefore ball bearings are used in machines.