# Why is angular momentum conserved if we keep a ball on rough surface with only translational velocity after it attains pure rolling motion

Assume a ball to be kept on a rough surface with intial translational velocity V and no rotation. After some time it aquires pure rolling. It is acted upon by an external torque due to friction still the angular momentum of the ball does not change from that of the initial one. Why is this?

• Why do you say the angular momentum is conserved? – Manish S Dec 20 '20 at 14:02
• Angular momentum of an isolated system is always conserved. – my2cts Apr 5 at 12:57