CK-12 Physical Science Concepts - For Middle School

4.49. References http://www.ck12.org

4.49 References

1. Train: John H. Gray; Bike: Flickr:DieselDemon; Geese: Don McCullough; Meteor: Ed Sweeney (Flickr:Navicore).
   Examples of moving objects. CC BY 2.0


2. Bus: Flickr:torbakhopper; Children: Flickr:woodleywonderworks. We perceive motion based on our frame of
   reference. CC BY 2.0


3. Christopher Auyeung (CK-12 Foundation); Compass: Seamus McGill. Distance is an important component
   of maps. CC BY-NC 3.0; Compass: Public Domain


4. Christopher Auyeung (CK-12 Foundation); Compass: Seamus McGill. Direction is an important component
   of a map. CC BY-NC 3.0; Compass: Public Domain


5. Left: Kenny Louie; Right: Mario Roberto Duran Ortiz. Cars on a highway have a greater speed than cars in
   city traffic. Left: CC BY 2.0; Right: CC BY 3.0


6. Peter Lai. Position time graph for an object. CC BY-NC 3.0


7. Peter Lai. The slope of a position time graph is velocity. CC BY-NC 3.0


8. Christopher Auyeung (CK-12 Foundation); Compass: Seamus McGill. These objects are moving at different
   speed and in different directions. CC BY-NC 3.0; Compass: Public Domain


9. Carousel: Jef Fisher; Skydiver: User:Degrer/Wikimedia Commons; Runner: Mike Spille; Basketball: Maurice
   Dayao/U.S. Navy. Examples of acceleration. Carousel: CC BY 2.0; Skydiver: Public Domain; Runner: CC
   BY 2.0; Basketball: Public Domain


10. Richard Greenwood (Flickr: rsgca). Bicyclist accelerating on a downhill stretch. CC BY 2.0


11. Christopher Auyeung. Velocity versus time graph for a sprinting race. CC BY-NC 3.0


12. Image copyright Leah-Anne Thompson, 2013. Scooter rider pushing off the ground. Used under license from
    Shutterstock.com


13. Christopher Auyeung. Representation of a force using an arrow. CC BY-NC 3.0


14. Christopher Auyeung. This physics book is at rest because it has balanced forces. CC BY-NC 3.0


15. Mathew Cerasoli, modified by CK-12 Foundation. Tug of war illustrating the concept of net force. CC BY
    2.0


16. Laura Guerin. Two soccer players illustrating the concept of net force. CC BY-NC 3.0


17. Laura Guerin. Workers illustrating the concept of net force. CC BY-NC 3.0


18. Chris Down/Tango project(book), Arman Cagle (arrow), modified by CK-12 Foundation. Practice problem
    illustrating the concept of net forces. Public Domain


19. Left: Joy Sheng; Right: Jeremy Burgin. Two useful applications of friction. Left: CC BY-NC 3.0; Right: CC
    BY 2.0


20. Left: David Amsler (Flickr:amslerPIX); Right: Daniel Oines (Flickr:dno1967b). Two unwanted examples of
    friction. CC BY 2.0


21. Foil: User:MdeVicente/Wikimedia Commons; Magnified surface: Courtesy of NIST. Even smooth-looking
    surfaces like aluminum foil are very bumpy. Public Domain


22. Gregory Moine. Ice skates help reduce friction. CC BY 2.0


23. Karl Baron. Matches are lit using friction. CC BY 2.0


24. Ray Sawhill. Friction helps this person to walk. CC BY 2.0


25. Image copyright Ramona Heim, 2013. Ball bearings reduce friction. Used under license from Shutter-
    stock.com


26. Courtesy of Donna Dixon and the US Army. Parachutes work using fluid friction. Public Domain


27. Image copyright AVAVA, 2013. Practice problem illustrating how reducing friction can save energy. Used
    under license from Shutterstock.com


28. Image copyright Dja65, 2013. Weight being measured with a scale. Used under license from Shutterstock.com


29. User:Tó campos/Wikipedia. The moon is much closer to the Earth than the sun. Public Domain