$\newcommand{\vect}[1]{\mathrm{ \vec{\boldsymbol{#1}}}} $
Home Page
Next Page

Classical Mechanics
Conservation of Energy

We need a general approach if we want to obtain exact solutions.


Newtonian Formulation in Vector Notation

One-dimensional models are useful in cases where we have symmetries to exploit, but we need to rewrite Newton's Equation using vector calculus in order to encode directional information for general cases.


Energy Conservation from Newton's Eq. of Motion

$$ \begin{align} \vect{F} &= m \frac{dv}{dt} \\ &= m \frac{d \vect{v}}{d \vect{x}} \cancelto{v(t)}{\frac{dx}{dt}} \\ &= m \frac{d\vect{v}}{dx} \vect{v(t)} \\ &= m \frac{d\vect{v}}{dx} \frac{d ( \frac{\vect{v}^2}{2})}{d\vect{v}} \\ \vect{F} &= \frac{1}{2} m \frac{d}{dx} \left[\vect{v}^2\right] \end{align}$$