Unbalanced Forces
If resultant force is acting on an object, then it will accelerate. When a car starts moving, the thrust from the engine is much greater than the air resistance. The car accelerates. The faster the car moves, the greater air resistance acts.
Balanced Forces
When two or more than two forces are acting on a body causing no resultant force, we say that the forces are balanced.
As the following car goes faster, the air resistance increases until it is as big as the maximum thrust from the engine. The car is now moving with balanced forces.
If the resultant force acting on an object is zero, then it is said to be in equilibrium.
