2. FORCES TENSION, COMPRESSION, SHEAR, AND TORSION Mr. Ruddle Construction Technology

3. Lesson Overview In this lesson, you will analyze the four forces that can potentially act upon structural objects: tension, compression, shear and torsion. The lesson will prepare you to be able to select appropriate materials and designs for different situations based on the types of forces that need to be accounted for.

4. Objectives At the conclusion of this lesson, you will be expected to be able to:  1. Identify which forces are acting upon an object  2. Identify ways to counteract forces that may potentially affect objects  3. Analyze a design and determine a way to improve the way it handles forces.

5. Tension Pulling or Stretching force. http://www.cdli.ca/courses/isys1205/unit03_org01_ilo01/images/u3s4l1-04.jpg

6. Compression Pushing or Crushing force http://www.cdli.ca/courses/isys1205/unit03_org01_ilo01/images/u3s4l1-03.jpg

7. Shear Force applied parallel to the face of a material http://www.cdli.ca/courses/isys1205/phidgets/unit03_org01_ilo01/images/u3s4l1-06.jpg

8. Torsion Twisting or Turning force http://www.cdli.ca/courses/isys1205/unit03_org01_ilo01/images/u3s4l1-08.jpg

9. Forces as a Design Consideration  When designing objects, is important to consider the forces that the object might experience. Why ? http://www.youtube.com/watch?v=j-zczJXSxnw

10. Counteracting Forces http://media.techeblog.com/i mages/tunedmassdamper.jpg http://www.midas.com/Portals/0/A utoEd_Images/16_Steer_Suspension _IMG2.png http://www.giant- bicycles.com/images/technology_ maestro.jpg After considering potential forces, it is important to counteract those forces within your design. How are the forces being counteracted in the designs below ?

11. Vocabulary  Tension – Pulling/stretching force  Compression – Pushing/crushing force  Torsion – Twisting/turning force  Tuned Mass Damper – A device mounted to a structure that is used to counteract movement caused by various forces  Design Consideration – Something that needs to be taken into account when designing an object

12. Assessment On a sheet of paper, create four columns like you see below. Next, find 15 objects in this room that are experiences one of the four forces we discussed today and list them in the appropriate columns. Be prepared to share your findings! TensionCompressionTorsionShear

13. Resources and Practice  Visit the following website and be prepared to discuss it tomorrow. http://www.diydoctor.org.uk/projects/f orces.htm http://www.diydoctor.org.uk/projects/f orces.htm  Complete the “Checking for Understanding” sheet for tomorrow