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

7

They are stretchy

You can pull them.

8

Try

Different forces on a stretchimal

What happens?

9

Forces on a stretchimal

Before a force is applied - flat on table 10 newton

force on stretchimal

What would happen with

a smaller force?

a larger force?

10

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.

11

Stretchimals

Different shapes Same force What will happen?

12

Forces on stretchimals

Whatshape hasthe bluelizard,

whenstretched?

Before a force is applied

Flat on a table

10 newtons

13

Now for some tests !

14

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

15

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

18

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 !

19

Springs are useful

Forces

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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)

21

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 3

Images © Salinas Valley Memorial Healthcare

Forces can do amazing things!

Science saves lives