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.