Simple Machines

1
Simple Machines

• Thursday-Friday, Jan 7-8, 2007
• Get 4 note cards for todays lecture
• Please put your name on all 9 of your note cards.
• Hmwk Bring items for your Rube-Goldberg Machine
  a Box

2
Warm-Up

• Complete practice problems
• P 379 1, 2
• P 381 4 a,b

3
Upcoming Dates

• Friday, Jan 5 2nd per Assembly
• Tues., Jan 9, 6th per Assembly
• Mon., Jan 15, MLK day No school
• Tues/Wed, Jan 23,24 Test unit 5
• Friday, Jan 26 End of semester-early release

4
Why do we use machines?
Card 1 Back Machines multiply and redirect forces
Card 1 Front Why do we use machines?
5
Card 2 Back
Card 2 Front What are the 6 simple
machines? Give an example of each
6
Card 3 FrontWhat are the 3 types of levers?

• Card 3 Back
• Draw a picture of the 3 types of levers
• First class
• Second-class
• Third-class

7
(No Transcript)
8
The Lever Family

• Levers are divided into three classes.
• All first-class levers have a fulcrum located
  between the points of application of the input
  and output forces.
• In a second-class lever, the fulcrum is at one
  end of the arm and the input force is applied to
  the other end.
• Third-class levers multiply distance rather than
  force. As a result, they have a mechanical
  advantage of less than 1.
• Video clip D\Ch12\70613.html

9
The Lever Family, continued

• Pulleys are modified levers.
• Video clipD\Ch12\70614.html
• The point in the middle of a pulley is like the
  fulcrum of a lever.
• A single, fixed pulley has a mechanical advantage
  of 1.
• Multiple pulleys are sometimes put together in a
  single unit called a block and tackle.
• A wheel and axle is a lever or pulley connected
  to a shaft.
• The steering wheel of a car, screwdrivers, and
  cranks are common wheel-and-axle machines.

10
(No Transcript)
11
The Inclined Plane Family

• Inclined planes multiply and redirect force.
• An inclined plane turns a small input force into
  a large output force by spreading the work out
  over a large distance.
• A wedge is a modified inclined plane.
• A screw is an inclined plane wrapped around a
  cylinder. Video clip D\Ch12\70615.html

12
Compound Machines
Card 4 Back A machine made of more than 1 simple
machine. Examples of compound machines
are scissors, a car jack
Card 4 Front What is a compound machine? What is
an example of a compound machine?
13
Assignment Design a Rube-Goldberg machine

• Example of Rube-Goldberg machine
• http//www.rube-goldberg.com/
• Another example http//www.ebaumsworld.com/flas
  h/honda-ad.html
• Student examples http//www.mousetrapcontraption
  s.com/cool-machines-3.html

14

• As you raise spoon of soup (A) to your mouth it
  pulls string (B), thereby jerking ladle (C) which
  throws cracker (D) past parrot (E). Parrot jumps
  after cracker and perch (F) tilts, upsetting
  seeds (G) into pail (H). Extra weight in pail
  pulls cord (I), which opens and lights automatic
  cigar lighter (J), setting off sky-rocket (K)
  which causes sickle (L) to cut string (M) and
  allow pendulum with attached napkin to swing back
  and forth thereby wiping off your chin. After the
  meal, substitute a harmonica for the napkin and
  you'll be able to entertain the guests with a
  little music.

15
Milk man takes empty milk bottle (A), pulling
string (B), which causes sword (C), to sever cord
(D) and allow guillotine blade (E) to drop and
cut rope (F) which releases battering ram (G).
Ram bumps against open door (H) causing it to
close. Grass sickle (I) cuts a slice off end of
orange (J) at the same time spike (K) stabs
"prune hawk" (L). He opens his mouth to yell in
agony, thereby releasing prune and allowing
divers boot (M) to drop and step on sleeping
octopus (N). Octopus awakens in a rage and seeing
orange attacks it and crushes it with tentacles,
thereby causing all the juice in the orange to
run into glass(O).
16
Assignment

• By the end of class today
• Purpose of machine (must be appropriate)
• Sketch of machine with at least 5 steps (5 simple
  machines can be 5 different simple machines or 2
  levers and 3 ramps)
• List of group members and what each person in
  bringing to build machine.