Magnets and electromagnets lesson 4

TargetTo learn about variables, values and relationships in a magnets

investigation

September 23, 2009

Key words

Variable

Value

Relationship

What variables are there in a set of books?

colour of cover

size of the book

number of pages

pictures or not

colour of writing or black and white

What variables are there in a set of books?

What values are there?

Key words

Variable

Value

Relationship

= something that changes

= how the variable is measured

= a link between the variables

Notes

Let's look at some shapes:

What are the variables?

shape

size

colour

What are the values?

triangle or rectangle

small, medium or large

red or blue

What is the relationship between the shapes?

Discuss this with the person next to you.

Remember discussion is important.What do you think?

Let's look at some shapes:

What is the relationship between these shapes.

Shape – red shapes are squares, blue ones are triangles.

The next shape is blue. Can you predict the shape?

Yes = triangle

Let's look at another set of shapes:

What are the variables?

What are the values of these variables?

What is the relationship?

Shape, colour and size

Triangle or circle, red or blue, small or large

Let's look at another set of shapes:

What are the variables?

What are the values of these variables?

Can you make any connections or relationships?

Shape, colour and size.

Triangle or circle, red or blue, small or large.

Small = RedLarge = Blue

• 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.

Variables, values and relationships

What are the variables, values and relationships to the damage done to the

bridge in type of accident?

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 bridge Width of arm = metres

Relationships High speed = more damage High mass = more damage Stronger bridge = less damage Wider arm = less damage

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.

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?