Lecture04_Pushkar_2011_Jan24

# Lecture04_Pushkar_2011_Jan24 - PHYSICS 220 Lecture 04...

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Lecture 4 Purdue University, Physics 220 1 Lecture 04 Forces and Motion in 1 D Textbook Sections 3.2-3.6 PHYSICS 220

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Graphing calculator are not allowed during exams. Because they it can store nearly everything in memory. Lecture 3 Purdue University, Physics 220 2
Lecture 4 Purdue University, Physics 220 3 Mass and Weight Mass: quantifies the amount of inertia that an object possesses – an intrinsic property of the object Weight (Gravitational force exerted by the Earth) W = mg (g-acceleration due to gravity) g = GM earth /(r earth ) 2 = 9.8 m/s 2 (G – universal gravitational constant, more in Chapter 5)

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Lecture 4 Purdue University, Physics 220 4 Contact Forces Normal force: a contact force acting at an interface perpendicular to the surface of contact Frictional force: another contact force acting at an interface parallel to the surface of contact resist motion of the two surfaces sliding past each other always act opposite the direction of motion mg N F F f
Lecture 4 Purdue University, Physics 220 5 Friction Magnitude of frictional force is proportional to the normal force. F kinetic = μ k N μ k coefficient of kinetic friction F static μ s N μ s coefficient of static friction Be Careful! Static friction , can be any value up to μ s N Direction always opposes motion

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Friction and Walking The person “pushes” off during each step The bottoms of his shoes exert a force on the ground If the shoes do not slip, this force is due to static friction The shoes do not move relative to the ground
Lecture 4 Purdue University, Physics 220 7 Book Pushed Across Table Book sliding across table Isolate the object of interest (book)

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## This note was uploaded on 04/10/2011 for the course PHYS 220 taught by Professor Chang during the Spring '09 term at Purdue University-West Lafayette.

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Lecture04_Pushkar_2011_Jan24 - PHYSICS 220 Lecture 04...

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