Newton’s Second Law

Newton’s second law can be shown as the equation:

  • F = Resultant force in newtons (N)
  • m = Mass in kilograms (kg)
  • a = Acceleration in metres per second squared (m/s2)

This equation can also be rearranged, to form:

This equation shows that the acceleration of an object is:

  • Proportional to the resultant force acting on the object – The acceleration increases if the resultant force acting on the object increases.
  • Inversely proportional to the object’s mass – For a given force, the acceleration decreases if the mass of the object increases.

Inertial Mass

Inertial mass is a measure of how difficult it is to change an object’s velocity. We can calculate this by rearranging the equation from Newton’s second law, to form:

So the inertial mass is the ratio between force and acceleration.