> A rigid body is an idealization of a body that doesn't deform / change shape, formally speaking the distance between particles in the body remains unchanged when the body moves https://www.youtube.com/watch?v=4r_EvmPKOvY&t=2172s&ab_channel=blackedout01 https://www.brown.edu/Departments/Engineering/Courses/En4/notes_old/RigidKinematics/rigkin.htm https://chrishecker.com/Rigid_Body_Dynamics