When two forces act in the same direction, one needs to add these two forces. The overall force is the net force acting on the object.
By definition, a force is a push or pull exerted on an object. The Newton is the unit of measurement one uses to denote the strength of a force. Likewise, a vector can represent a force. A vector is a line with an arrow, where the length of the arrow denotes the force amount, and the arrow point represents the direction.
Depending on the amounts and directions of forces exerted on an object, one can either add or subtract these forces. If two forces are in the same direction, then one adds them to find the net force, which is the vector sum of these forces. However, when two forces act in opposite direction, one has to subtract the lesser force from the larger one to find the resulting force. The resultant is the direction of the larger of these two forces.
When two forces are opposite and equal in amount, the net force is zero. These two opposite forces are called balanced forces because they do not cause a change in the object’s motion. If two forces acting on an object are different in amounts, then they are unbalanced forces and will affect the object’s motion.
A combined force.
http://wiki.answers.com/Q/What_is_it_called_when_t...

The strongest force will push the other object in
http://www.chacha.com/question/whathappenswhent...

First, it should be noted that this situation can occur with or without a preemption system, and drivers should always be aware of this possibility.
http://www.prioritycommand.com/FAQs.html

Balanced Force, only if it is equal force (:
http://wiki.answers.com/Q/Equalsized+forces+that+...
