Drehradius

Drehradius is a geometric and kinematic term used to denote the radius of rotation, the distance from the axis about which a body rotates to a point of interest on or within the body. In planar motion with a fixed rotation axis, points describe circular paths whose radii equal their Drehradius relative to that axis.

Geometrically, the Drehradius corresponds to the perpendicular distance from the rotation axis to the point. In more general motion, the instantaneous center of rotation provides a local reference, and the Drehradius is the distance from that instantaneous axis to the point.

In equations, the tangential velocity v of a point is v = ω r, where ω is the angular velocity and r is the Drehradius. For a point undergoing rotation about a fixed axis, radial (centripetal) and tangential accelerations are a_c = ω^2 r and a_t = α r, with α the angular acceleration.

Applications include mechanical design of rotating bodies (disks, pulleys, gears), robotics and kinematics for linkage analysis, vehicle dynamics where turning radii influence stability, and biomechanics for joint rotation analysis. Measuring the Drehradius helps estimate speeds, forces, and energy in rotating systems.

See also: Radius of rotation, Instantaneous center of rotation, Rotational kinematics, Polar coordinates.