Machines

1. Machines Practice #1—Introduction to Machines Mr. Burleson geaux15@hotmail.com

2. Agenda • Introduction and Rules • Basics of Simple Machines • Simple Machines Practical • Homework *huge thanks to Alan Chalker (National Physics Chair) and Roger Demos (National Event Supervisor) for their support 2

3. Tips forScience Olympiad • Study often because all the work is done by you! • Use Teamwork for studying and practicing • Use the references, homework, and homework generators to practice • Know the rules better than anyone. • Check the national website often for updates and FAQs. • Practices are for covering material, sample tests, and practicing measurements—studying should be done at home • More practice will lead to better results

4. Introduction and Rules • Come prepared to practices with completed homework and all your questions • Listen and participate. • Be willing to study on your own and do more work than assigned 4

5. Machine Practice Timing Recommendations • Each Practice should be an hour to an hour and a half, once a week. • 15 minutes—Grading homework. • 30 minutes—Learning Lesson of the Day • 15 minutes—In Practice quick test on Lesson of the Day • 25 minutes—Practical testing • 5 minutes—Sending out homework • Each student who misses Practice should get the notes and homework to be ready for the next Practice or they will receive zeros for both. 5

6. Machines (B)Rules • Team of 2 • No Eye Protection Required • Device must be impounded • Part 1 (Written Test) • 45% of score • Simple Machine Concepts • Simple Machine Calculations • Simple Machine History is no longer included • Part 2 (Device Testing) • 55% of score • Two Ratio Scores (15% each) • One Time Score (15%) • Chart Score (10%) • Only five types of machines • Levers (all three classes) • Inclined Plane • Wedge • Pulley (up to two double pulleys) • Wheel and Axle • Prohibited topics • Compound machines • Dynamic Calculations • Material Strengths • Potential/Kinetic Energy • Coefficient of Friction • Screw Simple Machines • Angle of Repose 6

7. Machines (C)Rules • Team of 2 • No Eye Protection Required • Device must be impounded • Part 1 (Written Test) • 45% of score • Sim/Compound Machine Concepts • Sim/Compound Machine Calcs • Sim/Compound Machine History is no longer included • Part 2 (Device Testing) • 55% of score • Two Ratio Scores (15% each) • One Time Score (15%) • Chart Score (10%) • All six types of simple machines • Levers (all three classes) • Inclined Plane • Wedge • Pulley (up to two double pulleys) • Wheel and Axle • Screw • Prohibited topics • Dynamic Calculations • Material Strengths • Angle of Repose 7

8. Scoring forMachines • Exam Score (ES) is worth maximum 45 points (45 points awarded to highest test score) • Time Score (TS) = ((240-time)/240*15 points (max 15 points) • Ratio Score (R1 and R2)=(1-(abs(AR-MR)/AR))*15 points (max 2x15 = 30 points) • Chart Score (CS) is worth 10 points (max 10 points) • 2 points for including data spanning the possible mass range • 2 points for including at least 10 data points in each data series • 2 points for proper labeling (e.g. title, team name, units) • 2 points for distinct graphs (0.5 points each up to 2 points) • 2 point for including a labeled device diagram • Violations • Competition violate TS, R1, and R2 are multiplied by 0.9 • Construction violation, if resolved during competition block or miss impound TS, R1, and R2 are multiplied by 0.7 • Team with no device, no ratio estimate or do not make an HONEST attempt TS, R1, and R2 all marked zero • Final Score (FS)=ES+MS+TS+CS (maximum of 100 points) • Tie Breakers • Best ES score • Best TS score • Best R1 • Best R2 8

9. Your Binder is Your Lifeline • When you have two or more pictures of the same thing, include ALL of them (often Event Supervisors will get diagrams and samples from the internet) • When you solve a difficult problem, show all your work and put that in the binder to help remind you how you solved that difficult problem • Keep the binder small enough to be useful, but big enough to be comprehensive • Test you skills at finding things in the binder each practice so that it takes no more than 10 seconds to find anything • Make sure you can read it (good fonts) • Use sheet protectors when possible • 2” binder is new rule • A good binder is like having an open book test • Use your binder in all studying, practices, and at tournaments • Always build your own binder in case something happens to your partner’s • First page should be the rules, so you can find them quickly • Always have easy to read tables for constants, materials, and equations • Organize into sections that work for you and your teammate with tabs for easy finding • Focus on the things you have to look up or don’t understand • Include other tests with keys and work shown

10. Basics of Simple Machines • Lever • Inclined Plane • Wheel and Axle • Wedge • Pulley • Screw, not included in Simple Machines (B)

11. Basic Definition of Simple Machines • A simple machine is an elementary device that has a specific movement (often called a mechanism), which can be combined with other devices and movements to form a machine. • The idea of a "simple machine" originated with the Greek philosopher Archimedes around the 3rd century BC, who studied the "Archimedean" simple machines: lever, pulley, and screw • Thus simple machines are considered to be the "building blocks" of more complicated machines. • A bicycle has wheels, levers, and pulleys 11

12. Mechanical Advantage • A simple machine has an applied force (or effort) that works against a load force. • If there are no friction losses, the work done on the load is equal to the work done by the applied force. • This allows an increase in the output force at the cost of a proportional decrease in the distance moved by the load. • The ratio of the output force to the input force is the mechanical advantage of the machine.

13. Efficiency • Machines lose energy through friction, deformation and wear, which is dissipated as heat. • This means the power out of the machine is less than power in. • The ratio of power out to power in is the efficiency η of the machine, and is a measure of the energy losses.

14. What is a Lever? • A lever is a machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum • The word comes from the French lever, "to raise", cf. a levant. • A lever amplifies an input force to provide a greater output force, which is said to provide leverage. • The ratio of the output force to the input force is the ideal mechanical advantage of the lever.

15. Classes of Levers • Class 1: Fulcrum in the middle: the effort is applied on one side of the fulcrum and the resistance on the other side • A crowbar or a pair of scissors. • Class 2: Resistance in the middle: the effort is applied on one side of the resistance and the fulcrum is located on the other side. • A wheelbarrow, a nutcracker, a bottle opener or the brake pedal of a car. Mechanical advantage is greater than 1. • Class 3: Effort in the middle: the resistance is on one side of the effort and the fulcrum is located on the other side • A pair of tweezers or the human mandible. Mechanical advantage is less than 1.

16. IMA of Lever/Law of the Lever • If a and b are distances from the fulcrum to points A and B and let the force FA applied to • A is the input and the force FB applied at B is the output, the ratio of the velocities of points A and B is given by a/b, so we have the ratio of the output force to the input force, or mechanical advantage, is given by 16

17. In Practice Quiz • Think of as many levers you can, including around the house, construction sites, school, etc. • Workshop tools • Garden tools • Kitchen tools • Think of as many places where you can lose efficiency with a lever 17

18. Things to consider • Winners prepare • No one knows this material naturally, those that prepare the best will do better. • Study and do homework before practice, use practice for asking questions • Plan on doing work on this a few times a week in addition to practice • Winners work together • Be a good partner • Work off each other strengths • Practice together • Event Supervisors are volunteers • They have given up their time to prepare for the competition, run the event, score, etc. • Some are more experienced than others • Some know the rules more than others • Be respectful and work with them • Always listen to instructions and read the test before you ask your questions • Different Event Supervisors ask the same question differently

19. Arguing an Illegal Question • Always make sure you read the question again to ensure it really is illegal. • Event supervisor might have old rules, but double check your rules first. • Ask for how to implement the question within the rules. • Remove the illegal items like capacitors/inductors/LEDs/etc. • Operate it as DC instead of AC. • Reference the specific rule, normally in section 3.d • Semiconductors include diodes, LEDs, transistors, OpAmps, and integrated circuits. LEDs, Diodes and OpAmps are now allowed in certain circumstances. • AC circuit theory includes frequency analysis, two or three phase power, capacitor/inductor reactance. But they can sometimes be made legal by switching to a DC system. • AC devices include transformers, rectifiers, others. Most will not work with DC. • Several items are only available for Division C and not for B

20. Practical • Each team will use a ruler and several small objects. • If you have something to balance the ruler on top of you can use that as your fulcrum, otherwise use your finger • First, balance the ruler on the fulcrum point • Is the balance point near the middle of the ruler • Note when the ruler is not near the balance point, how does it rotate • Second, start with the balanced ruler and then have the second person put two of the same small objects on the ruler to find where they balance • Third, start with a balanced ruler and then have the second person put two different small objects on the ruler to find where they balance 20

21. Suggested References • Websites: • Soinc.org Simple Machines/ Complex Machines Event pages • Scioly.org student forums / wiki / test exchange • Wikipedia (Simple Machines, Levers, Pulleys, etc.) • http://www.khanacademy.org/#Physics • Khan Academy Tutorial on Mechanical Advantage • Museum of Science and Industry Simple Machines online game • SEDL Simple Machines Online Textbook • Department of Navy - Basic Machines Textbook

22. How to use the Homework Generator • Homework generator is a Microsoft Excel workbook with multiple tabs • The tabs are broken down into levels (start with Level 1 and work your way up) • Work on accuracy first, so don’t start Level 2 until you can you do all of Level 1 with 100% accuracy at least three whole sheets • A good way to improve speed is to see how many problems or sheets you can do in 5 min (after you are accurate) • Some tabs have reference material, but most only have problems • The numbers used in problems are from a random number generator • If on a Windows machine you can refresh using F9 • You can also refresh by reopening the workbook, printing, or saving the file • Every time it is refreshed it randomly comes up with new problems and corresponding answer sheets.

23. Homework #1 • Do the Homework Generator problems for Levers Level 1 • Go through the house and write down as many of the six simple machines as you can at home. • We will study more levers next in depth. 23