Question

How dynamics differ from mechanics?

Answer 1

When one combines statics with kinematics, One gets "dynamics", the study of how forces cause motion and vice versa. That's a building block approach, hence bottom-up.Mechanics, on the other hand, is a broad umbrella name for any study that includes consideration of both displacements and forces.
.My understanding is that the word "dynamics" refers to a bottom-up approach whereas the word "mechanics" reflects a top-down approach. Let me explain.
If one considers forces without consideration of motion, the subject of study is called "statics". The converse, the study of motion without consideration of forces, is called "kinematics". When one combines statics with kinematics, One gets "dynamics", the study of how forces cause motion and vice versa. That's a building block approach, hence bottom-up.

Mechanics, on the other hand, is a broad umbrella name for any study that includes consideration of both displacements and forces. Here, fluid mechanics stands in contrast to solid mechanics. This is the top-down approach, with the word "fluid" being thought as a modifier to the broader word "mechanics".