Physics 2211: Lecture 26

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Physics 2211 Lecture 26
Extending Conservation of Energy Hookes
Law Elastic Potential Energy
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Review Conservation of Energy during Free Fall
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How about this situation?
1D motion on a track
2D projectile motion
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Connect together all the infinitesimals to get
conservation of energy between
any two points on the ski jump
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What about this projectile motion?
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Recap
Extension of Conservation of Energy
Next Lecture
Knight Section 10.4-5 Hookes Law
Elastic Potential Energy
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Physics 2211 Lecture 35
Hookes Law Elastic Potential Energy
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Some Vocabulary
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Experimental Fact Hookes Law
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Block slips when spring force on block exceeds
maximum static friction force
At what time does the block begin to slip?
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What force F holds the box at rest if it is
displaced a distance X?
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Elastic Potential Energy
since d(se)0
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Conservation of Energy
Elastic Potential Energy
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When the bob hangs vertically and moves in a
circle at constant v, the spring is stretched
from its natural length L by an amount s. Write
the total energy of the system without using the
quantity s.
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Ls
Must use plus sign to substitute in E
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A ½ N collar slides 6 cm down a smooth rod. The
unstretched length of the spring (k 300 N/m) is
4 cm. What is the speed of the collar when it
reaches the bottom?
1. 3.2 cm/s
2. 0 cm/s
3. 6.4 cm/s
4. does not reach the bottom
5. 1.8 cm/s
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Recap
Hookes Law Elastic Potential Energy
Next Lecture
Knight Section 10.6 Elastic Collisions