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Fundamentals

Force diagrams like the one shown depict the direction and strength of forces by vector arrows. Longer arrows mean stronger forces. One can determine if the forces are balanced by looking at the arrow size. Equal length arrows mean that the forces are balanced. Such situations are consistent with constant speed. 
 

There are four similar versions of this question. Two of the versions include:
 

Version 1:

The diagram below represents the forces acting upon a rightward-moving object. Each arrow represents a force; the length of the arrow represents the strength of the force.


Is this object speeding up, slowing down, or moving at a constant speed?
Is this object experiencing balanced forces or unbalanced forces?




Version 2:

The diagram below represents the forces acting upon a rightward-moving object. Each arrow represents a force; the length of the arrow represents the strength of the force.


Is this object speeding up, slowing down, or moving at a constant speed?
Is this object experiencing balanced forces or unbalanced forces?

 

How to Think About This Situation:

When considering how an object will move - whether it will accelerate or move with a constant speed and direction, it is important to compare the strength of the forces that act on the object. Forces, when unbalanced, cause objects to accelerate. And if an object accelerates, one can be assured that the forces acting on it are unbalanced. On the other hand, a balance of forces is consistent with an object maintaining a constant speed.


If all oppositely-directed forces are of the same strength, then those forces are said to be balanced. In such situations, the object does not speed up nor slow down. It maintains a constant speed.
 


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