PAGE EDITORS: Sarah Murray, Carolina Ribeiro, Daniel Clavijo, Mack Shoer, and Ariela Zebede

Natland Note: (8/18/13)

  • Notes look good!
  • show solutions to sample problems
  • also show some of the other sample problems & solutions that I gave out
  • still need links to other good websites, video links/posts, a self-created video, images from other sites, some more animations from physics classroom with descriptions, etc.


NOTES:
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This question is helpful in understanding the graphs of kinetic energy when an object is launched or dropped.


HELPFUL DIAGRAMS:



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This gif shows the law of energy conservation at work. Are there any nonconservative forces acting on the rollercoaster? Yes, the normal force. Is it doing work? No, because it is always perpendicular to the displacement. Therefore, the mechanical energy is constant throughout the motion. The bar labeled "KE" represents the kinetic energy, and the bar labeled "PE" represents the potential energy. Note how as one of them increases, the other decreases.
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This image explains how energy varies according to different spring positions. In position A, potential energy is very high because the spring is very stretched out. In position B, the spring gets closer to its equilibrium state, consequently causing a decrease in potential energy. In C, the spring is at its equilibrium state, so it has no potential energy. In D, the spring is compressed as much as it is stretched in position B, and therefore has the same potential energy of position B. Finally, in E, the spring is compressed as much as it is stretched in position A, and therefore has the same level of potential energy. Because the Mechanical Energy is not changing, the kinetic energy must vary with the potential energy so that both energies combined equal the total mechanical energy.
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Because this truck is not moving, all of its energy is in the form of potential energy.
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In this diagram, there are no nonconservative forces acting on the objects so the total mechanical energy always stays the same. The potential energy varies according to height, and the kinetic energy does the exact opposite in order for K+U to continue to equal the total mechanical energy.

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This gif shows that work does not change when the steepness or angle changes. However, the force does change when the angle changes.


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Right before the car on this roller coaster begins to plummet, the riders have their maximum potential energy. As they descend, their potential energy will decrease as their kinetic energy increases (they speed up)



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This image demonstrates visually the changing of potential energy and kinetic energy. It shows that as potential energy increases, kinetic energy decreases and vice versa, because although the normal force is acting on the object, it is not doing work and therefore no mechanical energy is lost.




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Here's a another good example of kinetic and potential energies. As the bowman pulls back on the string, he increases the elastic potential energy of the bow. Once he releases, that potential energy is turned into kinetic energy as the arrow speeds up and away from the bow.


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This graph shows force versus distance, illustrating the equation W = Fdcos(ɵ)


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This image shows the free body diagrams of an object when it is attached to a spring that is either in equilibrium, stretched or compressed.



This gif shows that kinetic energy is non-linear, making even a small increase in velocity significant in terms of energy.


This video offers a demonstration of Kinetic and Potential energy concepts.


A good example of how energy is conserved. The man would be putting his life at risk if the conservation of energy did not exist.



This video shows how hockey ties into work, energy, and power

gotta love Bill Nye!


Conceptual examples done in class: (from textbook)

Page 163 #1
Answer: F1 does more work than F2
Page 169 #5, 6, 7
Answer to #5: No. Kinetic energy is not changing and neither is potential energy, so no work is done.
Answer to #6: C. Negative work. Kinetic energy decreased, which means negative work was done.
Answer to #7: False. Height is also increasing so some of the work is put into potential energy.
Page 177 #10
Answer: All are true
Page 178 #14
Answer: E
Page 187 #2, 11, 13
Answer to #2: B
Answer to #11: C. Zero because displacement is zero.
Answer to #13: D

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work-it-t-shirt-53g.jpgCLASS T-SHIRT!






SAMPLE PROBLEMS:

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A) 11 m/s
B) No
C) 7.7 m/s


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A) 3.1113 m/s
B) .8206 m (to a height of .4939 m)

A) 11 m/s
B) No


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A) 0.6 m
B) 1.5 m/s



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Don't do part A
B) 66.885 J
C) 0.4572 m/s


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A) 7.5 J
B) 15 J
C) 7.5 J
D) 30 J




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A) 20 m along the bottom
B) 78.4 J



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The particle stops 20 cm (.20 m) from the left edge. This is because it takes the particle 2.5 passes over the rough part to finally stop.


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141.6169 m




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A) 5/2 R
Don't do part B

Solutions:

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Problem 29 Self-Created Video
http://www.showme.com/sh/?h=Rz7ULnk

HW 6.2 Solutions

#1
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#47
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#61
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#49
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AIRCRAFT CARRIER LAUNCH

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landing hook
Image result for landing on aircraft carrier cable
Image result for landing on aircraft carrier cable
Image result for landing on aircraft carrier cable
Image result for landing on aircraft carrier cable


taking off....steam powered catapult

Image result for aircraft carrier steam catapult
Image result for aircraft carrier steam catapult


Related image
Related image








WEBSITES:


http://physics.info/energy-conservation/
Provides both a summary of the topics and useful practice problems and resources.

http://www.physicsclassroom.com/class/energy/u5l2bc.cfm
Provides practice questions with useful animations, answers, and explanations

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/kinetic_energy/kineticact.shtml (a really easy to follow interactive activity about energy!)

http://hyperphysics.phy-astr.gsu.edu/hbase/work.html
This has nice examples and calculations showing applications of work, energy, and power.

http://science.howstuffworks.com/aircraft-carrier3.htm/printable
("Catapults and Aircraft Carriers")

http://www.ux1.eiu.edu/~cfruf/bio3002/energy_types.htm
This is a really cool roller coaster simulation, where you play with kinetic and potential energies on your track. The goal is to have the cart complete the total distance, while keeping your passenger healthy!

http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/Sarah_Schlichting/Energy.html
This explains kinetic and potential energy and also has a great animation that shows what happens to kinetic and potential energy when nonconservative forces act on an object.

MORE VIDEOS:
https://www.youtube.com/watch?v=eVl5zs6Lqy0
Shows the relationship between force, compression, and work done on a spring. This is useful to understand why the graph of force vs. X looks the way it does.


http://www.youtube.com/watch?v=OoJqCsHAak8 (2:00)
("Crash test 50 70 90". This shows a crash test done for a car at speeds of 50, 70, and 90 km/h. Yikes. Can help show the non-linear rate at which damage goes up with speed, fitting the expectation of the equation for kinetic energy)

SOURCES:

http://www.ux1.eiu.edu/~cfruf/bio3002/energy_types.htm (bow and arrow picture)
http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/shawna_sastamoinen/Velocity&Kinetic.htm (roller coaster photograph)
http://www.physicsb-2009-10.wikispaces.com (animations)
http://www.launc.tased.edu.au/online/sciences/PhysSci/done/kinetics/wep/Work.htm (force-distance graph)
http://www.arborsci.com/cool/swing-set-newtonian (Science teacher swing cartoon)
http://www.nerdytshirt.com/view-all-math-shirts.html (WORK IT shirt)
http://www.animations.physics.unsw.edu.au//jw/work.htm (Car braking distance animation)

www.physicsclassroom.com (images with energy measurements)