The second law is that a mass acted on by a force undergoes an acceleration in the direction of the force, with a magnitude inversely proportional to the mass and proportional to the force. It is represented by the formula F equals ma, where F equals the force, M equals the mass and A equals the acceleration. This illustration shows the effect of a force being applied to a mass. Notice how it produces a steady increase in speed. Now let us decrease the mass and increase the force. Notice how it produces a faster increase in speed. Now let us increase the mass and decrease the force. Notice how it produces a slower increase in speed. In conclusion, all changes in motion are based on this law. This includes both changes in speed and direction. It is indeed fundamental to understand emotion. Because without it, changes in motion cannot be properly understood.