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Bell Ringer 1-26-10

Bell Ringer 1-26-10. In your own words, write a complete sentence defining the word “force.”. Force Chapter 10 Sections 1 and 2. Force. A force is a push or a pull. Like velocity and acceleration, a force is described by its strength AND direction.

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Bell Ringer 1-26-10

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  1. Bell Ringer 1-26-10 In your own words, write a complete sentence defining the word “force.”

  2. ForceChapter 10 Sections 1 and 2

  3. Force • A force is a push or a pull. • Like velocity and acceleration, a force is described by its strength AND direction. • The SI unit for force is the newton ( N ).

  4. Net force • Net force = the combination of ALL the forces acting on an object. • The net force determines whether an object moves and in what direction.

  5. Combining Forces •  = -- 5 N 5 N 10 N • Add forces acting in the same direction • -- =  5 N 10 N 5 N • Subtract forces acting in opposite directions. • The force goes in the direction of the greater force. •   = 0 5 N 5 N • If forces are equal and they go in opposite directions, they can cancel each other out.

  6. Balanced Forces • Equal forces acting on one object in opposite directions = balanced forces. • Each force is balanced by the other. • When forces are balanced there is NO movement. (NO net force)

  7. Unbalanced forces • Unbalanced forces are NOT balanced and this causes an object to start moving, stop moving, or change direction. • Unbalanced forces result in a net force and cause a change in the object’s motion.

  8. Friction • Friction= the force that two surfaces exert on each other when they rub against each other. • The strength of friction depends on (1) how hard the surfaces push together and (2) the types of surfaces involved.

  9. Friction Foldable • Once your paper is folded, label the four sections with the four types of friction: • Static friction • Sliding friction • Fluid friction • Rolling friction p. 342

  10. Types of friction • Static friction – friction that acts on objects that are not moving Ex. Pushing on a heavy refrigerator/ driving off with a book on top of the car • Sliding friction – friction that occurs when 2 solid surfaces slide over each other Ex. Bike brakes/ ballet dancers

  11. Types of Friction (cont’d) • Rolling friction- occurs when an object rolls across a surface (ex: skateboard on road) • Fluid friction – occurs when a solid object moves through a fluid (ex: surfboard on water)

  12. Exit Quiz 1-26-10 • What is a force? • The combination of all the forces acting on an object is called ______. • If two forces are balanced, is there a net force? • The SI unit for force is the ________. • Tell me one of the four types of friction and give an example.

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