Newton's Law of Motion (Newton's Second Law)

What happen if the resultant of force in an object is not equal to zero? If that’s the case, the object’s velocity will change. It will increase if the direction of resultant of force is in line with that of the object’s velocity. On the contrary, the velocity will decrease if the resultant of force is in opposite to that of the object’s velocity. The relationships of resultant of force and acceleration can be explained based on Newton’s law II, i.e.:

If the resultant of force working on an object is not equal to zero, the object will experience an acceleration, which direction is in line with that of the resultant of force.

Mathematically, Newton’s Second law can be written as follows

∑F = ma    or    F = ma

Where F is the magnitude of force, m is the object’s mass, and a is the acceleration experienced by the object.

A person playing snowboard esperiences acceleration due to external force working on her, e.g. her hands propelling force, the friction force, and the earth's gravity