SPRINGS

Stretching and bouncing !

2

Snake in a box

As the tin opens

the snake pops out

as the spring is released.

What is inside?

snake

spring

3

Stetching

Pull

Pull harder

hold

hold

4

Stop pulling and --- Elastic materials

spring back into shape.

Plastic materials stay stretched.

(Like plasticine)

5

Lets find out - - -

6

Stretchimals have different shapes

Thick

Thin

Long

Short

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They are stretchy

You can pull them.

8

Try

Different forces on a stretchimal

What happens?

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Forces on a stretchimalBefore a force is applied - flat on table 10 newton

force on stretchimal

What would happen with

a smaller force?

a larger force?

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Forces are measured in newtons

The weight of an apple is about 1 newton.

The weight of a bag of sugar is 10 newtons.

When you stand on the floor it is pushing up with a force of about 40 newtons.

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Stretchimals

Different shapes Same force What will happen?

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Forces on stretchimals

Whatshape hasthe bluelizard,

whenstretched?

Before a force is appliedFlat on a table

10 newtons

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Now for some tests !

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Re-cap Different forces on the same

elastic –The larger the force- the larger the

stretch

Same force on different stretchimals- the fatter the stretchimal- the smaller

the stretch

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SPRINGS

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Toys with springs

The spring bends as the woodpecker pecks down the rod.

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Springs are often hidden Look around you.

paper clip

spring

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Beds often have springs The springs are

compressed when you lie on them

but are strong enough to support you.

Why must this be a very hard bed !

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Springs are usefulForces

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Springs save lives Blood must flow through our hearts. The blood flows through arteries Arteries become blocked Springs can be used to keep hearts

working.

Stents can be squeezed -

later the stent will open. A stent ( enlarged)

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Placing a stent in an artery

1. The squeezed stent is placed at the blockage.2. A balloon opens the stent.3. The stent keeps the artery open so the blood

can flow.

Step 1 Step 2 Step 3Images © Salinas Valley Memorial Healthcare

Forces can do amazing things!Science saves lives