Lecture07a - PHYSICS 149: Lecture 7 Chapter 2 2.8 Tension...

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PHYSICS 149: Lecture 7 • Chapter 2 – 2.8 Tension – 2.9 Fundamental Forces • Chapter 3 – 3.1 Position and Displacement Lecture 7 Purdue University, Physics 149 1
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Tension Definition: Magnitude of Contact Force between different segments of the string (or between an end and the object attached there) Example: T P T is the force on the left portion from the right portion |T| is the tension at point P NOTE: T can only pull the other object Lecture 7 3 Purdue University, Physics 149
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Tension Lecture 7 Purdue University, Physics 149 4 At any point in the rope (or string, cable or chain), tension is the pulling force exerted on the rope on one side of the point by the rope on the other side. At its two ends, tension is the pulling force exerted on the object attached to its ends by the ropes at the ends. Note that tension can pull but not push. “If” the chain’s weight is not negligible, T 1 > T 2 > T 3 > T 4 . For example, T 1 = T 4 + chain’s weight . =T 1 =T 2 =T 3 =T 4
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Ideal Cord An ideal cord has NO MASS Consequence: the tension is the same at ALL POINTS along the cord. Lecture 7 5 Purdue University, Physics 149
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Tension with “Ideal Cord” “Ideal cord”: a cord that has zero mass and thus zero weight In an ideal cord, (a) the tension has the same value at all points along the cord, and (b) the tension is equal to the force that the cord exerts on the objects attached to its ends (as long as there is no external force on the cord). Note: In many cases, the weight of a cord is negligibly small compared to the weight of the objects attached to its ends, and thus we may assume that it is an ideal cord. =T 1 =T 2 =T 3 =T 4 “If” the chain’s weight is negligible (ideal cord), T 1 = T 2 = T 3 = T 4 . Lecture 7 6 Purdue University, Physics 149
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Ideal Pulley Pulley: A pulley serves to change the direction of a tension force, and may also (in the case of multiple-pulley systems) change its magnitude. “Ideal pulley”: a pulley that has no mass and no friction.
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This note was uploaded on 04/23/2011 for the course PHYS 149 taught by Professor Staff during the Spring '08 term at Purdue University-West Lafayette.

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Lecture07a - PHYSICS 149: Lecture 7 Chapter 2 2.8 Tension...

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