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Magnets and electromagnets, lesson 4

### Transcript of Magnets L4

• 1. Magnets and electromagnets lesson 4 Target To learn about variables, values and relationships in a magnets investigation September 23, 2009

2. Key words Variable Value Relationship 3. Whatvariablesare there in a set of books? 4. colourof cover sizeof the book numberof pages picturesor not colour of writingor black and white Whatvariablesare there in a set of books? What values are there? 5. Key words Variable Value Relationship = something that changes = how the variable is measured = a link between the variables Notes 6. Let'slookat some shapes: What are thevariables ? shape size colour What are thevalues ? triangle or rectangle small, medium or large red or blue 7. What is the relationship between the shapes? Discuss this with the person next to you.Remember discussion is important. What do you think? 8. Let'slookat some shapes: What is the relationship between these shapes. Shape red shapes are squares, blue ones are triangles. Thenextshape isblue . Can youpredictthe shape? Yes= triangle 9. Let's look at another set of shapes: What are thevariables ? What are thevaluesof these variables? What is the relationship ? Shape, colour and size Triangle or circle, red or blue, small or large 10. Let's look at another set of shapes: What are thevariables ? What are thevaluesof these variables? Can you make anyconnectionsorrelationships ? Shape, colour and size. Triangle or circle, red or blue, small or large. Small = Red Large = Blue 11.

• A digger weighing 8 tons is on top of a flatbed trailer and heading east on Interstate 70 near Hays, Kansas. The extended shovel arm is made of hardened refined steel and the approaching overpass is made of commercial-grade concrete, reinforced with 1 inch steel rebar spaced at 6 inch intervals in a crisscross pattern layered at 1 foot vertical spacing.
• Solve: When the shovel arm hits the overpass, how fast do you have to be going to slice the bridge in half? (Assume no effect for headwind and no braking by the driver...)
• Extra Credit: Solve for the time and distance required for the entire rig to come to a complete stop after hitting the overpass at the speed calculated above.
• Answer - Who cares, the trucking company just bought themselves a bridge.

12. 13. 14. 15. Variables, values and relationships

• What are the variables, values and relationships to the damage done to the bridge in type of accident?

16. Answers Variables Speed of truck, mass of digger, strength of concrete on the bridge, width of movable arm on the digger Values Speed = mile per hour,Mass of digger = kilograms,Strength of concrete = Newtons per cm to crush the bridgeWidth of arm = metres Relationships High speed = more damageHigh mass = more damageStronger bridge = less damageWider arm = less damage 17. Investigating magnet strength Variables Values Shape and size of the magnet. Number or mass of paper clips picked up. Bar or horse shoe magnet, mass of magnet in grams. Number of paper clips. Method of testing add paperclips to the magnet until they fall off. Count the number of clips and record results on a table. 18. Investigating magnet strength Variables Values Shape and size of the magnet. Number or mass of paper clips picked up. Bar or horse shoe magnet, mass of magnet in grams. Number of paper clips. What do your results show? Is there a relationship between the variables?