Which joint rotates around an axis or center point?

• A. Prismatic joint
• B. Cylindrical joint
• C. Revolute joint
• D. Spherical joint

Answer: (C)

Rotational motion about a fixed axis is described by a revolute joint. It acts like a hinge, where the connected link swings around one fixed axis and its position is described by a single angle. That pure rotation about an axis matches the prompt’s idea of rotating around an axis or a central point.

A prismatic joint, by contrast, moves the link only linearly along a straight path with no rotation. A cylindrical joint does rotate, but it combines rotation with translation along the same axis, so the motion isn’t purely about a single axis. A spherical joint allows rotation about multiple axes through the joint center, offering several rotational freedoms rather than rotation about a single fixed axis.