... without looking: because that's the Law.can someone explain why angular momentum is conserved about O?
Angular momentum is a measure of an object's rotational motion. It is defined as the product of an object's moment of inertia and its angular velocity.
Angular momentum is calculated using the equation L = Iω, where L is angular momentum, I is moment of inertia, and ω is angular velocity.
The conservation of angular momentum states that the total angular momentum of an isolated system remains constant, unless acted upon by an external torque.
Torque is the rate of change of angular momentum. This means that an external torque acting on an object will cause a change in its angular momentum.
Some examples of angular momentum in everyday life include the spinning of a top, the rotation of a bicycle wheel, and the motion of a planet around the sun.