Question

why is a ball bearing used in cycle hub ?
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Answer 1

Explanation:

to reduce the friction....

Answer 2

$\huge\mathcal{Ball\: bearing✓✓}$

A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races.

$\huge\mathcal{Purpose✓✓}$

The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads.