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# Section 2

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### Section 2

1. 1. Friction and Gravity
2. 2. FrictionA Smooth Surface? If you look at the polished surface of an aluminum alloy under a powerful microscope, you’ll ﬁnd that it is actually quite rough.
3. 3. FrictionThe force that t wo surfaces exert on each otherwhen they rub together A Smooth Surface? If you look at the polished surface of an aluminum alloy under a powerful microscope, you’ll ﬁnd that it is actually quite rough.
4. 4. FrictionThe force that t wo surfaces exert on each otherwhen they rub togetherThe strength of the force of friction depends on 2things how hard the surfaces push together the types of surfaces involved A Smooth Surface? If you look at the polished surface of an aluminum alloy under a powerful microscope, you’ll ﬁnd that it is actually quite rough.
5. 5. Types of Friction
6. 6. Types of FrictionStatic Friction: Friction that acts on objects thatare not moving
7. 7. Types of FrictionStatic Friction: Friction that acts on objects thatare not movingSliding Friction: Occurs when t wo solid surfacesslide over eachother
8. 8. Types of FrictionStatic Friction: Friction that acts on objects thatare not movingSliding Friction: Occurs when t wo solid surfacesslide over eachotherRolling Friction: When object rolls across thesurface
9. 9. Types of FrictionStatic Friction: Friction that acts on objects thatare not movingSliding Friction: Occurs when t wo solid surfacesslide over eachotherRolling Friction: When object rolls across thesurfaceFluid Friction: Water, oil, other liquids cause theobject to move easily
10. 10. Static FrictionTo make the sled move, the athlete ﬁrsthas to overcome the force of static friction.Static friction acts in theopposite direction to theintended motion.Sliding FrictionOnce the sled is moving, itslides over the ﬂoor. Slidingfriction acts between the sledand the ﬂoor in the oppositedirection to the sledʼs motion.Rolling FrictionRolling friction occurs whenan object rolls over a surface.For the skateboarder, rollingfriction acts in the directionopposite to the skateboardʼsmotion.Fluid FrictionWhen an object pushes ﬂuidaside, friction occurs. The surfermust overcome the ﬂuid frictionof the water.Static frictionIntended directionof motionSliding frictionDirection of motionFluid frictionDirection of motion Rolling friction
11. 11. Gravity
12. 12. GravityStudyJams
13. 13. GravityStudyJamsGravity is a force that pulls objects toward eachother
14. 14. GravityStudyJamsGravity is a force that pulls objects toward eachotherNewton realized that Gravity acts everywhere inthe universe
15. 15. GravityStudyJamsGravity is a force that pulls objects toward eachotherNewton realized that Gravity acts everywhere inthe universeThe law of Universal gravitational states thatthe force of gravity acts bet ween all objects inthe universe
16. 16. Gravity Continued
17. 17. Gravity ContinuedTwo factors affect the gravitational attractionbet ween objects: Mass Distance
18. 18. Gravity ContinuedTwo factors affect the gravitational attractionbet ween objects: Mass DistanceForce also depends on the distance bet ween theobjects
19. 19. Gravity ContinuedTwo factors affect the gravitational attractionbet ween objects: Mass DistanceForce also depends on the distance bet ween theobjectsMass is the measure of amount of matter, not tobe confused with weight
20. 20. Gravity and Motion
21. 21. Gravity and MotionFree Fall: When an object is accelerating while itsfalling
22. 22. Gravity and MotionFree Fall: When an object is accelerating while itsfallingAir Resistance:
23. 23. Gravity and MotionFree Fall: When an object is accelerating while itsfallingAir Resistance:Terminal Velocity: is reached when the force ofair resistance equals the weight of the object
24. 24. Gravity and MotionFree Fall: When an object is accelerating while itsfallingAir Resistance:Terminal Velocity: is reached when the force ofair resistance equals the weight of the objectProjectile Motion: Something thrownhorizontally