Lecture
This lecture covers the concept of rotations in solid mechanics, focusing on two-dimensional rotations and the transition to three dimensions. The instructor explains the rotation around an arbitrary axis, the rotation matrix, and the relationship between small angles and rotation matrices. The lecture also delves into the use of matrices to represent the cross product and the importance of understanding rotations in different coordinate systems such as cylindrical and spherical coordinates. The session concludes with a discussion on the calculation of velocities and accelerations in cylindrical and spherical coordinates.