Bell Ringer 1-27-10

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# Bell Ringer 1-27-10 - PowerPoint PPT Presentation

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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### 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 10section 2friction and Gravity

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

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
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)
Who is this?

Sir Issac Newton

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