Newton's second law

Newton's second law of motion can be described by this equation:

Force = mass × acceleration

This is when:

  • force is measured in newtons (N)
  • mass is measured in kilograms (kg)
  • acceleration is measured in metres per second squared (m/s²)

The equation shows that the acceleration of an object is:

  • proportional to the resultant force on the object
  • inversely proportional to the mass of the object

In other words, the acceleration of an object increases if the resultant force on it increases, and decreases if the mass of the object increases.

Example

Calculate the force needed to accelerate a 22 kg cheetah at 15 m/s2.

Force = mass × acceleration

Force = 22 × 15

Force = 330 N

Question

Calculate the force needed to accelerate a 15 kg gazelle at 10 m/s2.

Force = mass × acceleration

Force = 15 × 10

Force = 150 N