Newton's 2nd law

This lesson addresses these specification points:

P2.15: Recall and use Newton's Second Law as force (newton, N) = mass (kilogram, kg) × acceleration (metre per second squared, m/s2)
F = m × a

P2.22: Explain that inertial mass is a measure of how difficult it is to change the velocity of an object (including from rest) and know that it is defined as the ratio of force over acceleration

Here are some useful resources:

Handy youtube clips

An interesting animation illustrating the effect of mass and force on acceleration