Net force is the product of mass and acceleration. The unit of force is newtons (N).
f = m × a.
The mass of an object is absolute – it is constant for a specific object or particle. However, the magnitude of weight is variable; it depends on gravitational field strength (location). Weight is the force acting upon an object due to gravity.
W = m × g
The weight component of an object parallel to the slope is given by sinθ; the component perpendicular to the slope is given by mgCosθ.
Free body diagrams can be used to isolate all the forces acting on a particular object.
| Weight | The gravitational force acting on an object through its centre of mass |
| Friction | The force that arises when two surfaces rub against each other |
| Drag | The resistive force on an object travelling through a fluid (the same as friction) |
| Tension | The force within a stretched cable or rope |
| Upthrust | An upward buoyancy force acting on an object when it is in a fluid |
| Normal contact force | A force arising when one object rests against another, |
equal to the component of the object’s weight parallel to the slope.
Each force vector is represented by an arrow labelled with the force it represents; each arrow is drawn to the same scale.