Law of conservation of angular momentum of a rigid body rotating on a fixed axis
Law of conservation of angular momentum of rigid body rotation.
Definition and overview:
Law of conservation of angular momentum of a rigid body rotating on a fixed axis
According to the angular momentum theorem of rigid body rotating around a fixed axis, if the resultant torque of rigid body rotating around a fixed axis is zero, that is
M=O
I= constant
When a rigid body rotates on a fixed axis, if the external force acting on the axis is zero (or not affected by the external torque), the angular momentum of the rigid body on the same axis remains unchanged. This is the law of conservation of angular momentum of a rigid body rotating on a fixed axis.
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(1) The moment of inertia of a single rigid body around a fixed axis is constant. If the resultant moment m of the external force to the axis is zero, the angular momentum of the rigid body around the axis is conserved, that is, the angular momentum I at any moment should be equal to the angular momentum Im at the initial moment. That is, Im =I, so @ = @. At this time, the object rotates at a constant speed around the fixed axis.
(2) When an object rotates around a fixed axis, if its moment of inertia to the axis is variable, under the condition of meeting the conservation of angular momentum, the angular velocity @ of the object changes with the change of moment of inertia, but the product I of the two remains unchanged, so when it becomes larger, @ becomes smaller; When it gets smaller, @ gets bigger. For example, when a ballet dancer performs.
(3) The free rotation of dumbbells on the turntable belongs to a special case of the law of conservation of angular momentum of the system rotating around a fixed axis. Because the gravity of people, the turntable and a pair of dumbbells, and the supporting force of the ground on the turntable are parallel to the rotating shaft, no torque is generated, M=0, so the angular momentum of the system should always remain unchanged.