CK-12 Physical Science - For Middle School

http://www.ck12.org Chapter 16. Work and Machines

Zip line: http://www.flickr.com/photos/tourismnewbrunswick/6088556853/; Crane: http://www.flickr.com

/photos/oimax/273930741/. Flag: CC BY-NC 3.0; Zip line: CC BY 2.0; Crane: CC BY 2.0

23. Sharada Prasad. http://www.flickr.com/photos/sharadaprasad/3668336064/. CC BY 2.0


24. Christopher Auyeung. CK-12 Foundation. CC BY-NC 3.0


25. Christopher Auyeung. CK-12 Foundation. CC BY-NC 3.0