15.2 :  固定軸を中心とした回転運動

When a rigid body rotates about a fixed axis, any given point within that body moves in a circular path around a specified line or point.

This type of rotation is defined by the angular position, represented by the angle θ which is measured from a fixed reference line to the rotating object.

The change from this angular position, quantified as a differential dθ, is termed angular displacement. The magnitude of this displacement can be measured in degrees, radians, or revolutions. Here, one revolution equal to 2π radians.

The right-hand rule gives the direction of angular displacement, which is along the axis of rotation.

Angular velocity, denoted as ω, describes the rate of change of angular displacement. Angular velocity is measured in units of radians per second.

Furthermore, angular acceleration, denoted as α, is the rate of change of angular velocity. It is measured in the units of radians per second squared.

Similar to angular displacement; both angular velocity and angular acceleration are vector quantities directed along the axis of rotation.