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Bell Ringer 1-27-10

Bell Ringer 1-27-10. See if you can answer these from memory: What is a force? What unit measures force? A ________ is a combination of all the forces acting on an object. List the two types of forces and the key words we use to remember them. Chapter 10 section 2 friction and Gravity.

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Bell Ringer 1-27-10

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  1. Bell Ringer 1-27-10 See if you can answer these from memory: What is a force? What unit measures force? A ________ is a combination of all the forces acting on an object. List the two types of forces and the key words we use to remember them.

  2. Chapter 10section 2friction and Gravity

  3. 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

  4. 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

  5. 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)

  6. Who is this? Sir Issac Newton

  7. Gravity • Gravity- a force that pulls objects toward each other • Ex: Earth pulling us toward it • Law of Universal Gravitation- the law that states that the force of gravity acts between all objects in the universe • Why don’t you feel the gravity between other objects and you?

  8. Gravity • Two factors affect Gravity: • 1. Mass • amount of matter in an object • Not affected by gravity • Greater the mass, greater the gravity • Ex: sun and planets • 2. Distance • Increase distance, decrease gravity

  9. Weight • Weight- the force of gravity on an object or person

  10. Air Resistance • Air Resistance- an upward force exerted on falling objects • It’s not the same for all objects. • The greater the surface area, the greater the air resistance.

  11. Terminal Velocity • Terminal Velocity- the greatest velocity a falling object reaches • Exists when the force of air resistance equals the weight of the object/or the force of gravity pulling down on the object • Air Resistance = Weight or Gravity

  12. Projectile • Projectile- an object that is thrown • Will an object that is thrown horizontally land on the ground at the same time as an object that is dropped?

  13. 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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