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Simple Machines and Work

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.

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Simple Machines and Work

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  1. Simple Machines and Work An interactive unit designed to guide the understanding of 7th grade students By Lucas Kraschnewski Simple Machines are those machines that are made up of only 1 machine !!! Are these devices simple machines????

  2. Directions This 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)

  3. Process • 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 Exam • Complete the Rube Goldberg project as your “Final”

  4. 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. Chapter 1 -Mechanical Advantage (MA) Definition: The number of times a machine multiplies your input force (effort) Index or How many times easier a job becomes because of using the machine 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!

  5. Mechanical Advantage (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

  6. Mechanical Advantage (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 You can use this formula for any of the simple machines Ramp Height Pulleys:Count the number of ropes that are supporting (attached) to the object being lifted Output Force Or Input Force Wheel and Axle:Wheel Radius Axle Radius

  7. Index 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!

  8. Work Person #1 is working because he is lifting up on the bar and the bar is moving up!! 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!!

  9. Index Ch. 3 - Power!!! 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 Question- Why is this considered a power tool? 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? 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!!

  10. 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! Which one will make your job the easiest? 10 meters 5 meters How can this machine make your job easier, but not reduce the amount of work you do????

  11. Inclined Planes B A 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

  12. Index Chapter 5 -Screws Definition: 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.

  13. Screws Look at those 2 “screws” you just created. What do you notice? *You should see that the purple screw has tighter threads!! Question: 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. Think About It!! Why do mountain roads wrap around the mountain and not just go straight up and over the mountain? Why do we have spiral staircases?

  14. Index Wedges Chapter 6 – What do doorstops, shovels, and axes all have in common?? Definition: a double inclined plane placed back to back

  15. Wedges Think about the difference between trying to dig up solid ground with a square shovel vs. a spade shovel. Which is easier to use? Why? Where are wedges used? -Knives The longer the ramp length, the easier the work becomes!! -Arrows -Screwdrivers

  16. Index Chapter 7 - Levers The end you push down on Resistance Arm Effort Arm The end the object being moved sits on 3 Types Fulcrum (Pivot Point) 1st Class 2nd Class 3rd Class Definition:Bar that pivots on a fixed point called the Fulcrum

  17. 1st Class Levers * Fulcrum is between the load and the Input Force* Load = Box (what is being moved) The Load and Input Forces move in opposite directions 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

  18. 2nd Class Levers Load and Input Force both move in the same direction!! Input Force Load Fulcrum *Load is between the fulcrum and input force* Again, a longer bar will make work easier, but the longer the bar is, the farther you must lift that bar Fulcrum Load Work amount isn’t reduced!! Input Force

  19. 3rd Class Levers Load Fulcrum Input Force * Input Force is between the Load and Fulcrum* WARNING: Your effort is actually going to be more than the load you are moving!!

  20. Index Chapter 8 - Pulleys Definition: 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 1. Fixed 2. Movable 3. Block & Tackle B. Changing the direction of the load

  21. Fixed Pulleys - Wheel does not move!! Advantage 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! Flag Pole Disadvantage You apply more force than the load weighs due to friction Curtain

  22. Moveable Pulleys - Wheel moves in same direction you lift on rope!! Disadvantage You must lift up on rope a long distance to move the object a very short distance Advantage Less force (effort) is required to lift object

  23. 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

  24. Index Chapter 9 – Wheel and Axle Definition: 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!!

  25. Wheel and Axle Gears = wheel and axle with teeth! * Great examples of how the small wheel (axle) turns many times compared to the larger wheel

  26. Unit Review 1. 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!!

  27. Final Project – Rube Goldberg Machines 1. What is a Rube Goldberg Machine? 2. Background info. on Rube Goldberg 3. What are my final project requirements? Would you want to try to enter the National Rube Goldberg Machine Contest???

  28. Rube Goldberg Machines Rubrics Click Image to View Project #1 Rubric Print Your Rubric!! Click Here for Project #2 Rubric

  29. References Print off ALL Rube Goldberg Project WS Begin working on Rube Goldberg Machines!! 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 Producer: Mr. Kraschnewski lil_krasch@hotmail.com

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