0.1 What is Mechanics
Mechanics is about forces and motion as applied to bodies.
Scientific theory is a concise summary of scientific ideas describing the results of experiments.
Classical Mechanics
-
fundemental theory that attempts to explain motion of all matter under the influence of all forces
-
the 'rules' of motion when forces act
- is not a theory of the forces themselves (e.g. Electromagnetism and Gravity)
Good Theory is a theory that must agree with experiment. For example Newton's Mechanics
-
fails at atomic and sub-atomic scales
- inconsistent with electromagnet theory
- fails to describe motion at high speed
(v/c ³ 0.1)
Why learn about Newton's Mechanics when we have better theories?
-
Practical Reason
- adequate for most problems. Newton's Laws follow from Quantum Theory as an approximation (rule of thumb)
- Theoretical Reason
- concepts introduced in Newton's Mechanics are preserved in new theories. Such as:
-
Energy and Momentum Conservation
- Space and Time Invariance