Balanced and Unbalanced Forces

• Balanced forces


  Equal in size and opposite in direction. When forces are balanced, there is no change in motion.
• Unbalanced forces


  Forces applied to an object in opposite directions that are not equal in size. Unbalanced forces result in a change in motion.
• Friction


  The force that opposes the motion or tendency toward motion of two objects that are in contact.
• Gravity


  A pull between two objects, for example, between an object and Earth.
• Balanced forces


  1. Forces are equal in size and opposite in direction

  2. No change in motion
• Unbalanced forces


  1. Forces applied in opposite directions are not equal in size

  2. Results in a change in motion (speed and/or direction)
• Balanced forces example


  • Heavy bucket pushed lightly - remained at rest
  • Forces cancelled out, no motion
• Unbalanced forces example


  • Pushing on object unequally in opposite directions - object moved in direction of smaller force
  • Pulling on object with different amounts of force in opposite directions - object moved in direction of greater pulling force
• Pushing on bucket with small force

  Friction force balanced the pushing force, bucket did not move
• Pushing on bucket with larger force

  Pushing force greater than friction force, bucket moved
• When forces acting on an object are balanced, there is no change in speed or direction
• To move something, unbalanced forces must be acting on it
• Friction resists motion or tendency toward motion between two objects in contact
• Gravity pulls objects toward each other, e.g. Earth pulls objects toward it
• Friction


  A force that opposes the motion or tendency toward motion of two objects that are in contact.
• What is a force?

  A push or pull that can cause an object to change its motion or shape
• What is friction?


  A force that opposes motion between two surfaces in contact
• What is an unbalanced force?

  A force that causes an object to accelerate or change direction
• What is a net force?

  The combination of all forces acting on an object
• What does "rest" mean in physics?


  When an object is not moving, not changing its position
• What is motion in physics?

  When an object changes its position, whether it's small or large
• What is gravity?


  The force that attracts objects with mass towards each other
• What is the force of gravity?

  The force the Earth exerts on an object or the force an object exerts on the Earth
• What is the difference between mass and weight?

  Mass is the amount of matter; weight is the force of gravity acting on an object