In his laws of motion, Isaac Newton made statements about the effect of balanced and unbalanced forces.
Newton’s First Law of Motion states that objects with balanced forces acting on them will stay at rest or stay in constant motion.
Newton discovered that objects will continue to do what they are doing until an unbalanced force acts on the object. From this we can determine that:
We can also determine that forces acting on an object can change the shape of the object, the speed of the object, and the direction in which the object is moving.
Newton’s Second Law of Motion states that when an unbalanced force acts on an object:
The unit of force is called the newton (N).
1 newton is defined as that unbalanced force which produces an acceleration of 1 m/s2 when it acts on a mass of 1 kg. An average-sized apple weighs about 1 newton.
Newton's Second Law of Motion can be written as the following relationship:
F = ma
F = unbalanced force
m = mass
a = acceleration
Note that when you use this relationship, F always stands for unbalanced force.