phys1441-spring08-030508-post

phys1441-spring08-030508-post - PHYS 1441 Section 002...

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Wednesday, Mar. 5, 2008 PHYS 1441-002, Spring 2008 Dr. Jaehoon Yu 1 PHYS 1441 – Section 002 Lecture #13 Wednesday, Mar. 5, 2008 Dr. Jae hoon Yu Static and Kinetic Frictional Forces The Tension Force Equilibrium Applications of Newton’s Laws Non-equilibrium Applications of Newton’s Laws Uniform Circular Motion
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Wednesday, Mar. 5, 2008 PHYS 1441-002, Spring 2008 Dr. Jaehoon Yu 2 Announcements • Term exam #2 – Wednesday, March 26, in class – Will cover CH4.1 – whatever we finish Monday, Mar. 24 • Colloquium today – 4pm in SH101 – Dr. M. Wiltberger, U. of Colorado, Boulder – Geospace Modeling
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Wednesday, Mar. 5, 2008 PHYS 1441-002, Spring 2008 Dr. Jaehoon Yu 3
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Wednesday, Mar. 5, 2008 PHYS 1441-002, Spring 2008 Dr. Jaehoon Yu 4 Special Project Reminder • Using the fact that g=9.80m/s 2 on the Earth’s surface, find the average density of the Earth. • 20 point extra credit • Due: Wednesday, Mar. 12 • You must show your OWN, detailed work to obtain any credit!!
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Wednesday, Mar. 5, 2008 PHYS 1441-002, Spring 2008 Dr. Jaehoon Yu 5 When the two surfaces are not sliding across one another the friction is called static friction . The resistive force exerted on The resistive force exerted on the object up to the time just before the object starts moving. the object up to the time just before the object starts moving. Static Friction
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Wednesday, Mar. 5, 2008 PHYS 1441-002, Spring 2008 Dr. Jaehoon Yu 6 The magnitude of the static frictional force can have any value from zero up to a maximum value. MAX ss f f MAX s f = 01 s μ << is called the coefficient of static friction . Magnitude of Static Friction Kinetic friction applies during the move!! sN F What is the unit? Once the object starts moving, there is NO MORE static friction!! None
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Wednesday, Mar. 5, 2008 PHYS 1441-002, Spring 2008 Dr. Jaehoon Yu 7 Note that the magnitude of the frictional force does not depend on the contact area of the surfaces . MAX s f = sN F μ
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Wednesday, Mar. 5, 2008 PHYS 1441-002, Spring 2008 Dr. Jaehoon Yu 8 Static friction opposes the impending relative motion between two objects. k f = 01 s μ << is called the coefficient of kinetic friction . Kinetic Friction Kinetic friction opposes the relative sliding motion motions that actually does occur. The resistive force exerted on the object during its movement. kN F What is the direction of frictional forces? opposite to the movement
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Wednesday, Mar. 5, 2008 PHYS 1441-002, Spring 2008 Dr. Jaehoon Yu 9 Coefficient of Friction What are these?
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Wednesday, Mar. 5, 2008 PHYS 1441-002, Spring 2008 Dr. Jaehoon Yu 10 What are the forces in this motion?
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This note was uploaded on 10/21/2009 for the course PHYS phys1441 taught by Professor Dr.jhaehoonyou during the Spring '08 term at UT Arlington.

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phys1441-spring08-030508-post - PHYS 1441 Section 002...

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