rigidsolidbody

A rigid solid body is an idealized object in which the distances between all pairs of points remain constant regardless of external forces or motions. In this model, internal deformations such as stretching, bending, or compression are neglected, so the shape of the body is preserved during motion.

In three-dimensional space a rigid body has six degrees of freedom: three for translating the chosen reference point (often the center of mass) and three for rotating about axes through that point. In planar motion, the motion reduces to three degrees of freedom. The configuration can be described by the position of the reference point and the orientation of the body.

Key mass properties include the total mass, the location of the center of mass, and the moment of inertia, which describes how mass is distributed relative to the chosen reference frame. The moment of inertia is represented by a tensor in general, simplifying to a scalar for simple rotations. The kinetic energy of a rigid body consists of translational energy of the center of mass and rotational energy about the center of mass, expressed through the mass, velocity of the center, and the angular velocity together with the inertia properties.

Equations of motion for rigid bodies, such as the Newton–Euler equations, govern how translation and rotation evolve under applied forces and torques. In the absence of external torques, angular momentum is conserved. Rigid-body dynamics are widely used in engineering, robotics, computer graphics, and physics to approximate the behavior of real objects when deformations are small or can be neglected.

Limitations include the inherent approximation that real materials deform under load; the rigid-body model is most accurate when deformations are negligible compared to overall motion.