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Simple Machines and Work. An interactive unit designed to guide the understanding of 7 th grade students. By Lucas Kraschnewski. Simple Machines are those machines that are made up of only 1 machine !!!. Are these devices simple machines????. Directions. - PowerPoint PPT Presentation
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Simple Machines Simple Machines and Workand Work
An interactive unit designed to guide the understanding of 7th grade students
Simple Machines are those machines that are made up of only 1 machine !!!
Are these devices simple machines????
By Lucas Kraschnewski
DirectionsDirectionsThis unit Simple Machines and Work is
divided into 9 chapters:
Each chapter will have a variety of learning opportunities for you to investigate each topic
including:
(These 5 links are not active, 9 links above are active)
ProcessProcess1. Starting with Ch. 1, proceed through each
unit in order until reaching the end of Ch. 9
2. Complete each chapter in the following order:
A. Read and examine the notes page
B. Watch a video on the topic (if available)
C. Apply your understanding by watching / completing the animations and/or simulations
D. Go to the provided links to gain a deeper understanding
E. Complete the short quiz on each topic to assess your knowledge and e-mail results to teacher
F. Print Lab worksheets provided : complete / turn in
3. After finishing Ch. 9, complete the Unit Exam4. Complete the Rube Goldberg project as your
“Final”
Chapter 1 -Mechanical Chapter 1 -Mechanical Advantage (MA)Advantage (MA)
Definition: The number of times a machine multiplies your input force (effort)
or
How many times easier a job becomes because of using the machine
Before beginning complete the pre-quiz to the right. Check your answers and then e-mail your results to your
teacher. Your score will not be a factor at this point.
If a machine has a MA of 4, that means the machine being used makes your job 4 times easier to do than if you did
that same job without the machine!
Index
Mechanical Advantage Mechanical Advantage (MA)(MA)
Question #1: If a box weighs 50 Newtons, how much force do you have to apply to the box to lift it or slide it?
Answer: 50 Newtons (That’s how heavy the box is!!)
Now, let’s say you use a pulley machine to lift the box. The box still weighs 50 Newtons, but you notice you don’t have to lift as hard? You only lift with 25 Newtons of force and the box still can be picked up off the floor.
Has the machine made your job easier? Yes
How much easier? 2 times easier or you only work ½ as hard!!
The MA of the Pulley is 2
Mechanical Advantage Mechanical Advantage (MA)(MA)
Can you calculate how much a machine will help you (determine the MA) before you actually use it??
YES !
Procedures to Calculate MA for the simple machines:
Inclined Planes: Length of Ramp
Ramp Height
Pulleys: Count the number of ropes that are supporting (attached) to the object being liftedWheel and Axle: Wheel Radius
Axle Radius
Output Force Input ForceOr
You can use this formula for any of the simple machines
Ch.2-What is Work???Definition: When a force is exerted on an object and that
object moves in the direction the force is being applied
Work = Force X Distance
How hard you push or pull on
the object
How far you move the
object
Machines never reduce the amount of work you do! They make the work easier by requiring you to apply less force,
but over a longer distance!
Index
Work Question: Who is working?
A. Person #1
B. Person #2
C. Both#1.
#2.
Person #2 is not working because he is lifting up on the weights, but they are not moving up!!
Person #1 is working because he is lifting up on the bar and the bar is moving up!!
Ch. 3 - Power!!!Why is this considered a power tool?
Because ….. This electric jackhammer will break apart the concrete faster than he could break the concrete apart by hand!
Definition: The rate (how fast or slow) at which work is done
If Josh and Bill both lift 150N of weight over their heads, to a height of 3 m while exercising, but Josh lifts that weight in 2 seconds and it take Bill 4 seconds, who does more work?
Question-Question-
Neither!! They do the same work (F X D or 150 X 3 = 450J) But….
Josh has more power because he does the same work in less time!!
Index
Chapter 4 – Inclined Planes
Definition: Sloping surface that connects 2 points
T / F If you want to slide the box up onto the table and not just lift it straight up onto it, using these inclined planes will reduce the amount of work you have to do?Will these ramps make your job easier? YES!
How can this machine make your job easier, but not reduce the amount of work you do????
10 meters
5 meters
Which one will make your job the easiest?
Index
Inclined Planes
Check It Out!!!* The longer the ramp, which is actually the distance from point A to point B in the diagram, the easier the work becomes (less
force).* You can apply less force to move the car up the ramp, but
you move the car a longer distance. The amount of work you do is the same with all 3 ramps. Remember: Work = Force X
Distance
A
B
Chapter 5 -ScrewsDefinition: An inclined plane wrapped in a spiral
Try this before moving on!!1. Make 2 right triangles of different lengths, but with the same height.
For example-
2. Bold the long edge of each inclined plane.
3. Wrap one of the triangles around the pencil.
4. Repeat step #3 with the second triangle on a second pencil.
Index
ScrewsLook at those 2 “screws” you just created. What do you notice?*You should see that the purple screw has tighter threads!!
Which screw would be easier to turn into a block of wood? Why?The purple screw, because it started as an inclined plane with a longer ramp, and you should have learned that the longer the ramp the easier your job becomes.
Question:
Why do mountain roads wrap around the mountain and not just go straight up and over the mountain?
Why do we have spiral staircases?
Think About It!!
Chapter 6 –What do doorstops, shovels, and axes all have in common??
Wedges
Definition: a double inclined plane placed back to back
Index
WedgesThink about the difference between trying to dig up solid ground with a square shovel vs. a spade shovel.
Which is easier to use? Why?
The longer the ramp length, the easier the
work becomes!!
Where are wedges used?
-Knives
-Arrows
-Screwdrivers
Definition: Bar that pivots on a fixed point called the Fulcrum
Fulcrum (Pivot Point)
1st Class
2nd Class
3rd Class
3 Types3 Types
Effort ArmResistance
Arm
Chapter 7 - LeversThe end you
push down on
The end the object being
moved sits on
Index
1st Class Levers
* Fulcrum is between the load and the Input Force*
Load = Box (what is being moved)
Input Force = Where you push on the bar (far right in this case)
The longer the Effort Arm is compared to the Resistance Arm, the easier the work becomes!!
Generally speaking: Longer bar = Easier work
The Load and Input Forces move in
opposite directions
2nd Class Levers
*Load is between the fulcrum and input force*
Load and Input Force both move in the same direction!!
Fulcrum
Load
Input Force
Fulcrum
Load
Input Force
Again, a longer bar will make work easier, but
the longer the bar is, the farther you must lift that
bar
Work amount isn’t reduced!!
3rd Class Levers
* Input Force is between the Load and Fulcrum*
Fulcrum
Input Force
Load
WARNING: Your effort is actually going to be more than the load you are moving!!
Chapter 8 - PulleysDefinition: A machine made with a rope or cable wrapped around a grooved wheel
Pulleys can make work easier by:
A. Reducing the amount of required effort force
B. Changing the direction of the load
1. Fixed2. Movable
3. Block & Tackle
Index
Fixed PulleysAdvantageAdvantage
Changes direction of load for you
For Example:
In a hayloft, you can lift bails up by pulling down on the rope, so you don’t need to climb a ladder each time!
DisadvantageDisadvantage
You apply more force than the load weighs due to friction
Flag
Pol
e Curtain
- Wheel does not move!!
Moveable Pulleys- Wheel moves in same direction you lift on
rope!!
Advantage
Less force (effort) is
required to lift object
Disadvantage
You must lift up on rope a long distance to move the object a very short distance
Block and Tackle Pulleys
- Combination of a fixed and movable pulley
-Very little effort is needed to lift objects
- Must pull rope very long distance to move object short distance
Chapter 9 – Wheel and Axle
DefinitionDefinition: Machine made of 2 attached circles, one being small and one being large in size
By turning the small circle (axle) a short distance, the larger circle (wheel) travels a long distance!!
Index
Wheel and AxleGears = wheel and axle with teeth!
* Great examples of how the small wheel (axle) turns many times compared to the larger wheel
Unit Review1. Check out the following websites and video as a review first.
2. Then complete the 2 quizzes on the right and print/email your results
-Remember –
No machine reduces the amount of work….they make the work easier!!
Final Project – Rube Goldberg Machines
1. What is a Rube Goldberg Machine?
3. What are my final project requirements?
2. Background info. on Rube Goldberg
Would you want to try to enter the National Rube Goldberg Machine Contest???
Rube Goldberg Machines Rubrics
Click Image to View Project #1 Rubric
Click Here for Project #2 RubricPrint Y
our
Rubric!!
ReferencesReferences
Click to see complete website reference list
Print : Student Activity Check List
Make sure you have e-mailed or printed evidence of completion of all 8 daily quizzes and the 2 Unit
Review Quizzes
Print o
ff ALL Rube
Goldberg Project WS
Begin working on
Rube Goldberg
Machines!!
Producer: Mr. Kraschnewski
lil_krasch@hotmail.com
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