Chapter 2 Review of Forces and Moments - Brown University

Swivel joints don’t often appear in 2D problems. When they do, they look just like a pinned joint.
Ball and socket joint Your hip joint is a good example of a ball and
socket joint. The joint prevents motion, but allows your thigh to rotate
freely relative to the rest of your body.
Reaction forces: Prevents any relative motion. There must be three
components of reaction force.
Reaction moments. Allows free rotation about all 3 axes. No reaction
moments can be present.
Ball joints don’t often appear in 2D problems. When they do, they look just like a pinned joint.
Slider with pin joint Allows relative motion in one direction, and
allows relative rotation about one axis
Reaction forces: Motion is prevented in two directions, but allowed in
the third. There must be two components of reaction force, acting
along directions of constrained motion.
Reaction moments: Relative rotation is prevented about two axes, but
allowed about a third. There must be two components of reaction
moment.