Hello, my name is Kristin. I have two questions for you
that I would like you to please answer.
1. Can you give me a definition of UNBALANCED FORCES?
2. Can you give me a definition of BALANCED FORCES?
Balanced forces are forces that add up to zero. If you are being acted on
by balanced forces you will not move. For example, if you are "floating"
in a swimming hole, the force of gravity pulling you down is "balanced" by
the buoyant force the water exerts to lift you up.
If you try to "float" on the air you will find the forces are "unbalanced",
that is they don't cancel each other out. The gravitational force exceeds
the buoyant force the air exerts to lift you up and you fall.
An airplane flies because the the wings generate lift (an upward force) to
counteract gravity. To make the airplane go up the forces must be
unbalanced (more lift than gravity). They must also be unbalanced for the
plane to descend (more gravity than lift). If the forces are balanced the
plane stays at its present altitude and you have a smooth ride.
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---Nathan A. Unterman
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Update: June 2012