Page 24 - SIMPLE MACHINES
P. 24
4. SCREW –
4 . SC R E W –
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• •A screw is another simple machine, which is an
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inclined plane wrapped around a cylinder. The inclined
i n c l i n e d p l a n e w r a p p e d a r o u n d a c y l i n d e r . T he i n c l i n e d
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plane forms ridges in a spiral along the
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cylinder. These ridges are called the threads of the
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screw. The distance between the threads is called
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"the pitch" of the screw.
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• •Screw is inserted into a piece of wood using a
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screwdriver. It is difficult to pull out a screw out of
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a p i e c e o f w o o d c o m p a r e d t o a n a i l . T hi s i s b e c a u s e
a piece of wood compared to a nail. This is because
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a screw is really an inclined plane that goes round
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a n d r o u n d . T hu s , i t ho l d s t hi n gs t o ge t he r , t hr o u gh a
and round. Thus, it holds things together, through a
l o n ge r d i s t a n c e w i t h a s t r o n ge r gr i p .
longer distance with a stronger grip.
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• •We use screws to do many jobs. Bolts are used to
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put together many small parts of complex machines,
p u t t o ge t he r m a n y s m a l l p a r t s o f c o m p l e x m a c hi n e s ,
r e v o l v i n g s t o o l s , b a s e s o f m o s t l i ght b u l b s . E v e n y o u r
revolving stools, bases of most light bulbs. Even your
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pen caps have screws.
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