Simple Machines – Inclined Plane, Wedge and Screw
•Look at the objects shown on these pages. Which of them would you call machines?
•Would it surprise you to find out that each is ____________________________________
______________________________________________________________________________
•As you learned in the last section, a machine helps you do work by ________________
______________________________________________________________________________
 There are six basic kinds of simple machines: ____________________________________
______________________________________________________________________________
•In this section, you will learn how the different types of simple machines help you do
work.
Inclined Plane
Have you ever had to lift something from a lower level to a higher level?
•The job is much easier if you have a ___________________________________.
•For example, a ramp makes it much easier to push a _____________________________
_____________________________________________________________________________.
•A ramp is an example of a simple machine called ________________________________.
•An inclined plane is _________________________________________________________.
How It Works
•An inclined plane allows you to exert your ____________________________________
______________________________________________________________________________
•As a result, the input force needed is ___________________________________________.
•The _________________force that you use on an inclined plane is the force with which
_____________________________________________________________________________.
•The _________________ force is the force that you would need to ___________________
______________________________________________________________________________
•Recall that this force is equal to ________________________________________________.
Mechanical Advantage
You can determine the ideal mechanical advantage of an inclined plane by dividing the
_____________________________________________________________________________.
•Ideal Mechanical Advantage =
 For example, if you are loading a truck that is ______ meter high using a ramp that
is_____ meters long, the ideal mechanical advantage of the ramp is ______ meters
÷______ meter, or __________.
•The inclined plane increases the force you exerted _______________________ times.
•If the height of the incline does not change, ______________________________________
of the incline will _____________________________________________________________.
•The _____________________ the incline, the _______________________ you need to
push or pull an object.
•Although the amount of work is the same whether you lift the boxes or push them up
the ramp to the truck, you need ______________________ when you use an inclined
plane.
•When you use a ramp, what happens to the distance over which you exert your force?
Wedge
•If you’ve ever sliced an apple with ______________________, pulled up
_________________________ or seen someone chop wood with ______________, you are
familiar with another simple machine known as _______________________________.
•A wedge is _________________________________________________________________
_____________________________________________________________________________.
•It might be helpful to think of a wedge, like the one shown below, as
_____________________________________________ (or sometimes two inclined planes
back to back) _____________________________________________________.
The Forces of a Wedge
•The __________________________________ exerted on a wedge results in
_______________________________ that can split the log.
•You have probably never given much thought to the zippers
on your clothes.
•But zippers use _________________________________________________
_________________________________________________________________.
How It Works
•When you use a wedge, instead of moving an object along the inclined plane, you
___________________________________________________________________________.
•For example, when an axe is used to split wood, the axe _________________________
__________________________ on the blade of the axe, which is ______________________.
•That force pushes ____________________________________________________________.
•The wedge in turn exerts _________________________________ at a 90° angle to its
slope, splitting the wood in two.
•Wedges are a part of your everyday life. For example, ___________________________
_______________________________.
 A __________________________________________________________________________
all make use of wedges.
Mechanical Advantage
•The mechanical advantage of the wedge and ___________________________________
are similar.
•The ideal mechanical advantage of a wedge is determined by ______________________
______________________________________________________________________________
•The ____________________________ and __________________________ a wedge is, the
_____________________________ its mechanical advantage.
•For example, the cutting edge of a ______________________________________________
is a wedge.
•When you sharpen a knife, you make the wedge ______________________________
and ______________________________ its mechanical advantage.
•That is why __________________________________________________ than dull knives.
Screws
•Like a wedge, a screw is a simple machine that is related __________________________
___________________________________________________
• A screw can be thought of as _________________________________________________
__________________________________________________________.
•This spiral inclined plane forms the ____________________________________________.
How It Works
•When you twist a screw into a piece of wood, you exert ___________________________
on the screw.
•The threads of a screw act like __________________________________________ to
_____________________________________________________ over which you exert the
input force.
•As the threads of the screw turn, they __________________________________________,
pulling the screw into the wood.
• ________________________ between the screw and the wood holds the screw in place.
•Many devices act like screws. Examples include _________________________________
_________________________________________________.
•Look at the jar lid in Figure 15.
•When you turn the lid, your ____________________________ is greatly
_________________________________because of the _______________________________
____________________________________________.
•The threads on the lid are pulled against the matching threads on the jar with a strong
enough force to ______________________________________________________.
Mechanical Advantage
•The _______________________________________________________ of a screw are, the
____________________________________________________________________.
•This is because the closer the threads are, the __________________________________
________________________to fasten it into a piece of wood.
•Your input force is applied over ___________________________________________.
•The longer input distance results in an _________________________________________.
•Think of the length around the threads as the length of the inclined plane, and the
length of the screw as the height of the inclined plane.
•The ideal mechanical advantage of a screw is ____________________________________
______________________________________________________________________________
A Paper Screw
•To make a paper model of a screw, cut out a triangle from a piece of paper.
•Tape the wide end of the triangle to a pencil. Then wind the paper around the pencil.
Making Models How does this model represent a real screw? ______________________
_____________________________________________________________________________
Can you think of a way to calculate the ideal mechanical advantage of your model
screw?
______________________________________________________________________________
What is the mechanical advantage of your model screw? ___________________________
______________________________________________________________________________
•The length around the threads of a screw is the same as the
–height of an incline plane.
–width of an incline plane.
–length of an incline plane.
–output distance of an incline plane