Simple Machine: wheel and axle, pulley and screw

1
Simple Machine wheel and axle, pulley and screw

• Group FF

2
Wheel and Axel

• Josephine Harper

3
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)

4
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

5
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)

6
Mechanical advantage

• MAR/r
• Suppose the Radius of the wheel is 9ft and the
  axle has radius of 3ft.
• 9ft/3ft 3ft

7
Compound Machine 1

• Wheel and Axle
• Lever

8
Compound Machine 2

• Screws
• Wheel and Axle
• Lever
• Pulley

9
Compound Machine 3

• Lever
• Screws
• Wheel and axle
• Wedge

10
More wheel and axles
11
bibliography

• (1) http//www.usoe.k12.ut.us/curr/science/sciber0
  0/8th/machines/sciber/machine7.htm (explains the
  wheel and axle)
• (2) http//www.worsleyschool.net/science/files/whe
  el/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)

12
Pulley

• By Donald Heist IV

13
Definition of a Pulley

• Its 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.

14
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.)

15
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 ropes 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.

16
A single rope pulley
17
A 5 chain pulley
18
A 7 belt driven pulley
19
Bibliography

• http//teacher.scholastic.com/dirtrep/Simple/pulle
  y.htm
• http//www.uark.edu/depts/aeedhp/agscience/simpmac
  h.htm
• http//www.school-for-champions.com/science/machin
  es.htm

20
Screw A Simple Machine

• Justin Riegel

21
What Is It?

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

22
Mechanical Advantage

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

Mechanical Advantage Circumference Pitch
23
How Force Is Affected

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

24
Compound 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.

25
Compound 2 Scissors

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

26
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.

27
Bibliography

• http//en.wikipedia.org/wiki/Screw
• Found basic information and the definition of a
  screw
• http//inventors.about.com/od/sstartinventions/a/s
  crewdrivebr.htm
• Found about different types of screw and
  history of screws
• http//www.northerntool.com/webapp/wcs/stores/serv
  let/category_6970_941483771365
• http//science.jrank.org/pages/4058/Machines-Simpl
  e-Screws.html
• http//www.uark.edu/depts/aeedhp/agscience/simpmac
  h.htm
• Found how and the equation for finding the
  mechanical advantage of a screw