If you're seeing this message, it means we're having trouble loading external resources on our website. To log in and use all the features of Khan Academy, please enable JavaScript in your browser. Donate Login Sign up Search for courses, skills, and videos. Physics library. Rotational kinematics. Learn what angular displacement, angular velocity, and angular acceleration mean, as well as the relationship between them.
Angular motion variables Opens a modal. Relating angular and regular motion variables Opens a modal. Relationship between angular velocity and speed Opens a modal. Rotational kinematic formulas Opens a modal.
It makes no assumptions about constant rotational velocity. The net torque about an axis of rotation is equal to the product of the rotational inertia about that axis and the angular acceleration, as shown in Figure 1. If no outside forces act on an object, an object in motion remains in motion and an object at rest remains at rest. With rotating objects, we can say that unless an outside torque is applied, a rotating object will stay rotating and an object at rest will not begin rotating.
If a turntable were spinning counter clockwise when viewed from the top , and you applied your fingers to opposite sides the turntable would begin to slow its spinning. From a translational viewpoint, at least, there would be no net force applied to the turntable. The force that points to one side would be cancelled by the force that points to the other. Skip to main content. Rotational Kinematics, Angular Momentum, and Energy.
Search for:. Conservation of Angular Momentum. Conservation of Angular Momentum The law of conservation of angular momentum states that when no external torque acts on an object, no change of angular momentum will occur. Learning Objectives Evaluate the implications of net torque on conservation of energy. Key Takeaways Key Points When an object is spinning in a closed system and no external torques are applied to it, it will have no change in angular momentum.
The conservation of angular momentum explains the angular acceleration of an ice skater as she brings her arms and legs close to the vertical axis of rotation. If the net torque is zero, then angular momentum is constant or conserved. Key Terms quantum mechanics : The branch of physics that studies matter and energy at the level of atoms and other elementary particles; it substitutes probabilistic mechanisms for classical Newtonian ones.
Rotational Collisions In a closed system, angular momentum is conserved in a similar fashion as linear momentum. Learning Objectives Evaluate the difference in equation variables in rotational versus angular momentum. Which is the moment of inertia times the angular velocity, or the radius of the object crossed with the linear momentum. In a closed system, angular momentum is conserved in all directions after a collision. Since momentum is conserved, part of the momentum in a collision may become angular momentum as an object starts to spin after a collision.
Key Terms momentum : of a body in motion the product of its mass and velocity. Licenses and Attributions.
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