Simple Machine: wheel and axle, pulley and screw

Group FF

Wheel and Axel

Josephine Harper

What is a Wheel and Axel?

A wheel and axle is a lever that rotates in a circle around a center point or fulcrum.(1)

How does it work?

The radius of the wheel is larger than the axle so the force is spread to the axle, which has a smaller radius. The initial force is smaller then the resulting force.(2)

R/r

How does it change the force?

Work = Force × Distance Since the wheel is always larger than the

axle, effort applied to the wheel will always move further than the load at the axle.(3)

Mechanical advantage

MA=R/rSuppose the Radius of the wheel is 9ft

and the axle has radius of 3ft.

9ft/3ft = 3ft

Compound Machine #1

Wheel and AxleLever

Compound Machine #2

ScrewsWheel and AxleLeverPulley

Compound Machine #3

LeverScrewsWheel and axleWedge

More wheel and axles

bibliography

(1) http://www.usoe.k12.ut.us/curr/science/sciber00/8th/machines/sciber/machine7.htm (explains the wheel and axle)

(2) http://www.worsleyschool.net/science/files/wheel/andaxle.html (work of a wheel and axle)

http://www.fi.edu/pieces/knox/automaton/wheel.htm (give examples of wheel and axles and a description)

http://www.mikids.com/SMachinesWheels.htm (explains the wheel and axle)

(3) http://encarta.msn.com/encyclopedia_761562392/wheel_and_axle.html (a description of the wheel and axle and its benefits)

Pulley

By: Donald Heist IV

Definition of a Pulley

• It’s a wheel with a lip that allows you to transmit power from the ground to a higher place such as a roof or a tree it also allows for a change in direction by the means of a belt, cord, rope, or chain.

Ideal mechanical advantage

• Variables: • P = Load (number of

pennies) • P(actual) = Actual Load • P(calc) = Calculated Load • N = Number of Ropes

(Mechanical Advantage) • P = Pa x N • F = Friction • F = P(actual) - P(calc.)

How a pulley changes the forceand an example of mechanical

advantages

• Change in direction• To have less force you must pull on the

rope or chain a longer distance.• The number of vertical rope’s except for

the one your pulling on is your mechanical advantage.

• So if there is 5 vertical ropes including the one you are pulling on then your mechanical advantage would be 4.

A single rope pulley

A 5 chain pulley

A 7 belt driven pulley

Bibliography

• http://teacher.scholastic.com/dirtrep/Simple/pulley.htm

• http://www.uark.edu/depts/aeedhp/agscience/simpmach.htm

• http://www.school-for-champions.com/science/machines.htm

Screw: “A Simple Machine”Screw: “A Simple Machine”

Justin RiegelJustin Riegel

What Is It?What Is It?

A screw is one of six simple machines. A screw is one of six simple machines. It usually turns rotational force into linear It usually turns rotational force into linear force, but can also do the opposite. It is force, but can also do the opposite. It is mainly used to hold stuff together. It is a mainly used to hold stuff together. It is a modified version of an inclined plane.modified version of an inclined plane.

Mechanical AdvantageMechanical Advantage

An advantage of a screw is that the more threads An advantage of a screw is that the more threads the more advantage. Another plus is if threads are the more advantage. Another plus is if threads are closer together which also goes along with more closer together which also goes along with more threads. Mechanical advantage is the threads. Mechanical advantage is the circumference divided by the pitch. Pitch is the circumference divided by the pitch. Pitch is the number of threads in 1 inch of the screw.number of threads in 1 inch of the screw.

Mechanical Advantage =

Circumference Pitch

How Force Is AffectedHow Force Is Affected

A screw changes force, because the longer the A screw changes force, because the longer the screw the more you will have to turn it to screw the more you will have to turn it to make it tight.make it tight.

Compound #1: BicycleCompound #1: Bicycle

• One example of a compound machine is a bicycle. The wheels and pedals are wheel and axles. The brake handles are levers, and the seat adjustment is a screw.

Compound #2: ScissorsCompound #2: Scissors

Scissors are also a compound machine. Scissors are also a compound machine. It has levers as handles. Which then are It has levers as handles. Which then are squeezed to close the blades that are squeezed to close the blades that are wedges. But a screw completes it by wedges. But a screw completes it by holding the two pieces together.holding the two pieces together.

Compound #3: Locking Pliers

• On a pair of locking pliers the handles act as levers. The adjusting bolt acts as a screw to adjust the diameter size of the pliers.

BibliographyBibliography

http://en.wikipedia.org/wiki/Screwhttp://en.wikipedia.org/wiki/Screw

Found basic information and the definition of a Found basic information and the definition of a screwscrew

http://inventors.about.com/od/sstartinventions/a/http://inventors.about.com/od/sstartinventions/a/screwdrivebr.htm screwdrivebr.htm

Found about different types of screw and history of Found about different types of screw and history of screwsscrews

http://www.northerntool.com/webapp/wcs/stores/servlet/http://www.northerntool.com/webapp/wcs/stores/servlet/category_6970_94+1483+771365category_6970_94+1483+771365

http://science.jrank.org/pages/4058/Machines-Simple-http://science.jrank.org/pages/4058/Machines-Simple-Screws.htmlScrews.html

http://www.uark.edu/depts/aeedhp/agscience/simpmach.htmhttp://www.uark.edu/depts/aeedhp/agscience/simpmach.htm

Found how and the equation for finding the Found how and the equation for finding the mechanical advantage of a screwmechanical advantage of a screw