Newton's Second Law of Motion

Newton’s Second Law of Motion - a net force gives rise to acceleration.

The acceleration of an object is directly proportional to the net force acting on it and is inversely proportional to its mass. The direction of the acceleration is in the direction of the applied net force.

       F
a =  -----     (Bold letters for vectors)
        m

By using a constant of proportionality set equal to 1 (possible since we have different units)

F = ma

SI (Systeme International)     1 Newton = 1 N = 1 kg m/s² or 1 kg m s ^-2

cgs                                           1 dyne = 1 g cm s ^-2 = 10 ^-5 N

British System                        1 lb = 1 slug ft s ^-2

Weight = mg on earth     g = 9.80 ms ^-2