Presentation on theme: "1. 2 3 PROCEDURES 4 What is this for? 5 Can you do this instead?"— Presentation transcript:
4 What is this for?
5 Can you do this instead?
6 If you do this instead of this, you can continue your work while you wait for me. Do this today and at other times when you must wait.
7 Got it?
8 Share information at your table. Create your own Frayer diagrams in your own journal. 2 Frayer diagrams per page. USE THE RESOURCES AT YOUR TABLE to find out more, and to help you if you get stuck. (e.g. Your resources tell all you need to know to start learning about mechanical advantage.)
9 Copy this template for a Frayer diagram. Topic by your name
10 FIRST ASSIGNMENT Use the notes provided to make n Frayer diagrams to tell about any n of the following topics. n = ___ Inclined Plane Wedge Screw Lever 1 st Class Lever 2 nd Class Lever 3 rd Class Lever Wheel and Axle Pulley Fixed Pulley Movable Pulley Block and Tackle Simple Machines in Your Body Compound Machines
11 Make a Frayer Diagram Inclined Plane A flat, sloped surface aka: ramp How it works: allows you to exert your input force over a longer distance, thus decreasing input force Input force – force with which you push or pull the object Output force – force that you would have needed to just lift the object MA = length of incline/height of incline The longer the incline, the less input force you need fD Fd
12 Make a Frayer Diagram Wedge A device that is thick at one end and tapers to a thin edge at the other end One or two inclined planes put together Most often used to cut things How it works: you move the wedge toward the object, input force pushes wedge into object and the output force is the wedge exerting force on the object (e.g. chopping wood) MA = length of wedge/width of wedge The longer and thinner the wedge, the greater its MA fD Fd Examples: hand-held pencil sharpener, shovel blade, knife
13 Make a Frayer Diagram Screw An inclined plane wrapped around a cylinder (spiral forms threads of screw) How it works: twist a screw into wood (input force), the threads increase the distance over which the input force acts, the threads exert an output force on the object, friction holds the screw in place Input force is decreased by the threads MA = length around threads/length of screw The closer together the threads, the greater the MA fD Fd Examples: bolts, light bulbs, jar lids, some pumps
14 Make a Frayer Diagram Lever A rigid bar that is free to pivot, or rotate, on a fixed point (fulcrum) How it works: you exert an input force on one part of the bar and the other part of the bar exerts an output force on an object (opening a paint can) MA = input arm length/output arm length Input arm length – distance from fulcrum to input force Output arm length – distance from fulcrum to output force Levers can increase/decrease your input force and decrease/increase the output distance Classes of levers – according to the location of the fulcrum relative to input and output forces
15 Make a Frayer Diagram – First class lever Changes direction of input force f and d stay same if fulcrum is in center Can decrease input force if fulcrum is closer to output force (e.g. paint-can opener) Can increase input force if fulcrum is farther from output force Ex: paint-can opener, scissors (2), pliers (2), seesaw fD Fd
16 Make a Frayer Diagram – Second class lever Does not change the direction of the input force Increases output force Ex: wheelbarrow, door, nutcrackers (2), bottle openers – (Wheelbarrow also has a wheel and axle.) fD Fd
17 Make a Frayer Diagram – Third class lever Does not change the direction of the input force Increases output distance lever is attached to fulcrum Ex: hockey stick, fishing pole, baseball bat, catapult Fd fD
18 Make a Frayer Diagram Wheel and Axle Simple machine made of two circular or cylindrical objects fastened together that rotate about a common axis Object with larger radius wheel Object with smaller radius axle How it works: apply input force to wheel, axle rotates and exerts output force Increases force, but you must exert your force over a larger distance fD Fd Ex: doorknob, steering wheel, screwdriver Reverse: – Apply input force to axle (Fd fD) – Ex: transportation vehicles (cars, bicycles) MA = radius of wheel/radius of axle The greater the difference between the wheel and axle, the greater (or if reverse situation, lesser) the MA
19 Make a Frayer Diagram Pulley A simple machine made of a grooved wheel with a rope or cable wrapped around it How it works: you pull on one end of the rope (input force), the other end of the rope pulls on the object (output force) Can decrease amount of input force needed (fD Fd) Can change the direction of input force (d and f stay same) Types of pulleys
20 Make a Frayer Diagram – Fixed Pulley Pulley is attached to a structure (pulley does not move) Only changes the direction of the force F and D do not change MA = 1 Ex: flagpole, weightlifting machine
21 Make a Frayer Diagram – Movable Pulley Pulley is attached to the object you want to move (pulley moves along rope/cable with the object) Decreases input force needed (fD Fd) MA = number of supporting strands Ex: pulleys on sailboats
22 Make a Frayer Diagram – Block and Tackle Combines fixed and movable pulleys Decreases input force needed (fD Fd) MA = number of supporting strands Ex: construction crane
23 Make a Frayer Diagram Simple Machines in the Body Most are levers made of bones and muscle Muscles pull on bones (input force), joint is fulcrum, output force is used for doing work like lifting your hand Wedges – your teeth and fingernails
24 Make a Frayer Diagram Compound Machines A machine that utilizes two or more simple machines MA = product of MAs of individual simple machine parts Most machines are compound, e.g. apple peeler, pencil sharpener, bicycle, wheelbarrow, tweezers, scissors