Subsection 2.4.4 Force
What is force? In simple terms, a force is a push or a pull.
More precisely, a force is a vector quantity which tends to produce an acceleration of a body in the direction of its application. This means that if you want a stationary object to move, you must apply a force to it to get it going. If you want to keep it moving, you need to continuously apply a force to it to overcome friction, which is itself a force. Forces can exist without motion too – when an object is stationary it’s usually because there are many forces acting on it which cancel each other out, leaving no net force acting on the object. Forces always occur in pairs. A push on an object is always accompanied by an equal and opposite force acting on the pusher.
In the English system of units, force is measured in pounds, tons, or long tons.
In the SI system, force is measured in newtons (\(\N{}\)) or kilonewtons (\(\kN{}\)). The newton is a derived unit, equal to the product of mass and acceleration.
\begin{equation*}
\N{} = \mathrm{kg}\cdot {\mathrm{m}}/{\mathrm{s}^2}
\end{equation*}
For estimation purposes, a newton is about a quarter of a pound.
