Simple Machines
Lever, Wheel & Axle, and Pulley
Levers
•Have you ever ridden on a ___________________ or pried open a paint can with an opener?
•If so, then you are already familiar with another simple machine called _______________.
•A lever is ____________________________________________________________________
•The fixed point that a lever pivots around is called ______________________________
How It Works
•To understand how levers work, think about using a paint-can opener.
•The opener rests against ________________________________________________________
_____________________________________________________________________________.
•The tip of the opener is _________________________________________________________.
•When you push down, you exert an ________________________________________________,
and the opener ____________________________________________________.
•As a result, the tip of the opener _____________________________________, thereby exerting
an ______________________________________________________________________.
Mechanical Advantage
•A lever like the paint-can opener helps you in _______________________________.
•It ______________________________________________________ and it _______________
______________________________________________________________________________
•When you use the paint-can opener, you push the handle ________________________________
________________________ in order to move the lid __________________________________
_________________________________.
However, you are able to _________________________________________________________
______________________________________________________________________________
•The ideal mechanical advantage of a lever is determined by ______________________________
__________________________________________________by _________________________
______________________________________________________________________________
•A lever’s input distance and output distance determine its ideal mechanical advantage
•In the case of the paint-can opener, the distance from the fulcrum to the ___________________
is ___________________than the distance from the fulcrum to the ________________________.
•This means that the mechanical advantage is ____________________________________.
Different Types of Levers
•When a paint-can opener is used as a lever, the fulcrum is located _________________________
______________________________________________________________________________
•But this is not always the case.
•As shown in Figure 17, there are __________________ different types of levers.
•Levers are classified according to __________________________________________________
______________________________________________________________________________
•First-Class Levers
•First-class levers ______________ change the direction of the input force.
•If the _______________________________ to the output force, these levers also
___________________________.
•If the fulcrum is ___________________________________________, these levers also
_________________________________________.
•Other examples include ____________________________________________________.
•Second-Class Levers
•These levers ____________________________________, but __________________________
_________________________________of the input force.
•Other examples include _________________________________________________________.
•Third-Class Levers
•These levers ______________________________________, but ________________________
___________________________________of the input force.
•Other examples include ___________________________________________________.
•Which point on a lever set-up does not move?
–the fulcrum
–the point where the input force is applied
–the point where the output force is applied
–the mid-point
Wheel and Axle
•It’s almost impossible to insert a screw into a piece of wood with _________________________.
•But with a ________________________________, you can turn the screw easily.
• A screwdriver makes use of a simple machine known as the _____________________________.
A wheel and axle is a simple machine made of _____________________________or cylindrical
objects _______________________________________________________________________.
•The object with the _____________________________________ is called ________________
and the object with the ________________________________ is called the _________________.
•In a screwdriver, the ___________________________________________________________
___________________________________________.
•A __________________________________and a ____________________________________
are also examples of a wheel and axle.
How It Works
•How does a screwdriver make use of a wheel and axle to do work?
• Look at Figure 18. When you use a screwdriver, you apply an ____________________________
_____________________________________________________________________________.
•Because the wheel is ________________than the shaft, or ______________, the axle
_________________and exerts a ________________________________________.
•The wheel and axle ________________________________________, but you must exert your
force over a ________________________________________________.
•A screwdriver increases force by exerting the __________________________ over a
____________________.
•What would happen if the input force were applied to ______________ rather than
_________________________?
• For the riverboat in Figure 19 on the next page, the force of the engine is applied to
______________________________________________________________________________
______________________________.
•The large paddle wheel in turn ____________________________________________________.
•In this case, the input force is exerted over __________________________________________.
•So when the input force is applied _______________________, a wheel and axle
_____________________________________________________.
In a riverboat paddle wheel, the _________________________________________. The output
force is _____________________________ the input force, but it is exerted over
___________________________________________________
Mechanical Advantage
•You can find the ideal mechanical advantage of a wheel and axle by _______________________
_____________________________________________________________________________
 A radius is ___________________________________________________________________.
• The _______________________ the ratio between the radius of the wheel and the radius of the
axle, the ____________________________________________________________.
•Suppose the radius of a screwdriver’s wheel is ____________ and its axle radius is ___________.
•The screwdriver’s ideal mechanical advantage would be ___________ ÷ _________, or _______.
Pulley
•When you raise a flag on a flagpole or when you open and close window blinds, you are using a
pulley.
•A pulley is ___________________________________________________________________
______________________________________________________________________________
How It Works
You use a pulley by _____________________________________________________________
•This is _____________________________________.
•At the other end of the rope, _____________________________________________________
______________________________________________________________________________
•To move a heavy object over a distance, a pulley can make work easier in ___________________.
•First, it can __________________________________________________needed to lift the
object.
•Second, the pulley can __________________________________________________________.
•For example, you _______________________ on the flagpole rope, and the flag moves ______.
Types of Pulleys
•There are _____________ basic types of pulleys.
•A pulley that you _________________ to a structure is called a __________________________.
•Fixed pulleys are used at the tops of _______________________________________.
•If you attach a pulley to _________________________________________________________,
you use a ______________________________________.
•_____________________________________________ often use movable pulleys.
•By combining fixed and movable pulleys, you can make a _______________________________
called a ________________________________________________.
•The ideal mechanical advantage of a pulley is equal to __________________________________
______________________________________________________________________________
•When a pulley is attached to the object being moved it is called a
–block and tackle.
–fixed pulley.
–movable pulley.
–second-class pulley.