For a point mass, the moment of inertia is just the mass times the square of perpendicular distance to the rotation axis, I = mr 2. The moment of inertia must be specified with respect to a chosen axis of rotation. It appears in the relationships for the dynamics of rotational motion. Moment of inertia is the name given to rotational inertia, the rotational analog of mass for linear motion. This is called precession, and is analogous to the orbit of a mass under a central force. This changes its direction but not its magnitude, causing the tip of the axle to trace out a circle. If a spinning wheel and axle is supported by one end of the axle, then the torque produced by the weight of the wheel and axle produces a torque that is perpendicular to the angular momentum of the wheel.
Acting perpendicular to the velocity, it provides the necessary centripetal force to keep it in a circle. With the appropriate balance of force, a circular orbit can be produced by a force acting toward the center. This is because the product of moment of inertia and angular velocity must remain constant, and halving the radius reduces the moment of inertia by a factor of four. If the string is pulled down so that the radius is half the original radius, then conservation of angular momentum dictates that the ball must have four times the angular velocity. Using a string through a tube, a mass is moved in a horizontal circle with angular velocity ω. HyperPhysics***** Mechanics ***** RotationĬonservation of linear momentum dictates that when a mass strikes an equal mass at rest and sticks to it, the combination must move at half the velocity, because the product of mass and velocity must remain constant. Moment of Inertia Rotational-Linear Parallels More comparisons between linear and angular motion
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