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Basic Motions of a Rigid Body

Rigid-body translation, fixed-axis rotation, point velocities and accelerations, and transmission of rotational motion.

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This section covers rigid-body translation, rotation about a fixed axis, kinematics of body points, and transmission of rotational motion.

Basic motions of a rigid body are translation and rotation about a fixed axis. They are fundamental rigid-body kinematic models and also serve as components of more general motion.

Translation

In translation, every line fixed in the body remains parallel to its original direction. At any instant all points of the body have identical velocity vectors and identical acceleration vectors.

Fixed-axis rotation

The body configuration is described by an angular coordinate. Its time derivatives give angular velocity and angular acceleration, while the linear velocities and accelerations of body points depend on their distance from the axis.

Transmission of rotation

Mechanisms transmit rotational motion through gears, belts, friction drives, and other arrangements. Their kinematic relations connect the angular velocities of components through the geometry of the transmission.

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