Main variables:
\( \vec{x} = \) Position vector.
\( \vec{v} = \) Velocity vector.
\( \vec{a} = \) Acceleration vector.
\( t= \) Time.
\( |\vec{x}| = \) Magnitude of the position vector or distance.
\( |\vec{v}| = \) Magnitude of the velocity vector or speed.
\( |\vec{a}| = \) Magnitude of the acceleration vector.
Subindex ‘i’ means initial. Subindex ‘f’ means final. Example, \(\vec{v}_i\) means the initial velocity.
Main Equations:
Motion with constant velocity:
\begin{equation*}
\vec{x}_f = \vec{x}_i + \vec{v}_i t.
\end{equation*}
Displacement:
\begin{equation*}
\Delta \vec{x} = \vec{x}_f – \vec{x}_i.
\end{equation*}
Distance:
\begin{equation*}
|\Delta \vec{x}|.
\end{equation*}
Average velocity:
\begin{equation*}
\vec{v}_{av} = \frac{\vec{x}_2 – \vec{x}_1}{t_2 – t_1} = \frac{\Delta \vec{x}}{\Delta t}.
\end{equation*}
Instantaneous velocity:
\begin{equation*}
\vec{v}_{ins} = \lim_{\Delta t \rightarrow 0} \frac{\Delta \vec{x}}{\Delta t} = \frac{d\vec{x}}{dt}.
\end{equation*}
Average acceleration:
\begin{equation*}
\vec{a}_{av} = \frac{\vec{v}_2 – \vec{v}_1}{t_2 – t_1} = \frac{\Delta \vec{v}}{\Delta t}.
\end{equation*}
Instantaneous acceleration:
\begin{equation*}
\vec{a}_{ins} = \lim_{\Delta t \rightarrow 0} \frac{\Delta \vec{v}}{\Delta t} = \frac{d\vec{v}}{dt}.
\end{equation*}
Motion with constant acceleration:
\begin{equation*}
\vec{x}_f = \vec{x}_i + \vec{v}_i t + \frac{1}{2} \vec{a} t^2.
\end{equation*}
Velocity as a function of time:
\begin{equation*}
\vec{v}_f = \vec{v}_i + \vec{a} t.
\end{equation*}
Velocity as a function of the position and the acceleration:
\begin{equation*}
|\vec{v}_f^2| = |\vec{v}_i^2| + 2 \vec{r} \cdot \vec{a}.
\end{equation*}
Motion with constant acceleration as a function of the velocities:
\begin{equation*}
x = x_0 + \frac{1}{2} (v_i + v_f) t.
\end{equation*}