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SPRINGS
Stretching and bouncing !
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Snake in a box
As the tin opens
the snake pops out
as the spring is released.
What is inside?
snake
spring
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Stetching
Pull
Pull harder
hold
hold
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Stop pulling and --- Elastic materials
spring back into shape.
Plastic materials stay stretched.
(Like plasticine)
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Lets find out - - -
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Stretchimals have different shapes
Thick
Thin
Long
Short
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They are stretchy
You can pull them.
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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
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