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19. simple-machines-foldable-ppt-10-24-12.pdf

This document provides information about simple machines. It describes the six basic simple machines: inclined plane, lever, pulley, wedge, wheel and axle, and screw. It explains that simple machines make work easier by changing the amount of force needed, the distance over which force is applied, or the direction of the applied force. The document gives examples of each type of simple machine and discusses how compound machines are combinations of two or more simple machines. It also defines mechanical advantage as the ratio of output force to input force and efficiency as the ratio of output work to input work.

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Simple Machines (Making work easier…phew!)
Simple Machines Foldable • Line up your papers about 1-2 cm apart, so that you see “5, 6, 7, 8” along the bottom. • Fold the papers over so you see all 8 numbers in a row. 8.Changing Force 6. Screw 5. Wheel and axle 9.Mechanical Advantage and Efficiency 3. Pulley 2 Lever 1 Inclined Plane …making work easier and better  7.Compound/Complex Machine 4. Wedge
Simple Machines Foldable • On each tab, draw and describe that type of simple machine. • Then give 2-3 examples. • Make sure to include all of the information! 8 Simple Machine Notes 7 Lever 6 Pulley 5 Wheel & Axle 4 Wedge 3 Screw 2 Inclined Plane Draw & Describe: A sloped surface connecting a lower level to a higher level. Examples: A boat ramp, wheelchair ramp,propeller, ladder/stairs
What are MACHINES? • Most people think of complex, technical, or electronic gadgets with motors…, but machines can be much SIMPLER. • A machine is any device that lets you do WORK in an EASIER or BETTER way. • Basically: Simple machines make work EASIER.
How do machines do work? • Machines make work easier by changing 3 things about the FORCE you exert to do work:  AMOUNT OF FORCE you exert  DISTANCE over which you exert force  DIRECTION in which you exert force
What are SIMPLE MACHINES? • There are only 6 basic simple machines that make work easier: • Inclined Plane • Wedge • Screw • Lever • Wheel & Axle • Pulley
WORK & SIMPLE MACHINES • Simple machines DON’T change the amount of WORK done! (They change the size, distance or direction of your FORCE!) WORK IN = WORK OUT* (*usually machines lose a bit of work due to FRICTION…)
INCLINED PLANE • An inclined plane is a flat, sloped surface. It connects a lower level to a higher level. • You use less force over a longer distance to raise a load to a higher level. Input Force Output Force
INCLINED PLANE: Examples • Ramps (Boat ramps, wheelchair ramps) • Ladders/Stairs
LEVER • A lever is a bar that pivots or rotates on a point (called a fulcrum). • Levers may change the size, distance or direction of the force.
LEVERS: Examples & Uses • First Class Levers: – Scissors, See-saws, Pliers • Second Class Levers: – Staplers, Nutcrackers, Wheelbarrows • Third Class Levers – Shovels, baseball bats, tweezers
PULLEY • A pulley is a grooved wheel with a rope, used to raise/lower/move a load. • Pulley systems change the direction and/or decrease the input force so you can move heavier loads. Output Force Input Force Output Force Input Force
PULLEY: Examples & Uses • Cranes • Raising a flag on a pole • Window Blinds • Raising a sail on a boat • Clothesline
WEDGE • A wedge has slanting slides that meet at an edge – it splits material apart. • It changes force in one direction into a splitting force that acts at right angles to the blade. Input Force Output Force Output Force
WEDGE: Examples & Uses • Ax, Knife, etc. • Zippers • Used in all cutting machines (to split materials apart)
WHEEL & AXLE • The wheel is locked to the central axle – when one turns, so does the other one. • A short powerful force at the axle, will move the wheel’s edge a long distance. • A long motion at edge of wheel, moves the axle with great force. Input Force Output Force Output Force Input Force
WHEEL & AXLE: Examples & Uses • Screwdriver • Windmill • Cars/Bicycles • Rolling Pin • Door Knob • Fan
SCREW • A screw has a “thread” or “groove” wrapped around a central cylinder. • While turning, it converts a twisting force into a forward or backward force. Input Force Output Force
SCREW: Examples & Uses • Screws can holds things together or lift materials. • Screws • Screw top lids for jars/bottles • Light bulb • Swivel stools/chairs
Simple Machine Review! Write the name of the type of simple machine next to the picture.
COMPOUND MACHINES • Compound Machines – are made of combinations of two or more simple machines. • For example, a simple can opener is a combination of 3 simple machines: – Lever – Wheel & axle – Wedge
Machines make work easier by changing 3 things about the FORCE: • The amount of force • The distance of the force • The direction of the force
Machines make work easier by changing 3 things about the FORCE: • The amount of force (eg. A ramp lets you lift a heavy object with LESS force)
Machines make work easier by changing 3 things about the FORCE: • The distance of the force (eg. A baseball bat lets you move your arms a short distance, but move the end of the bat a large distance).
Machines make work easier by changing 3 things about the FORCE: • The direction of the force (eg. The pulley on a set of window blinds lets you move the blinds UP with a DOWNWARD pull.
What is the mechanical advantage of a machine? • A machine’s mechanical advantage is the number of times a machine increases a force exerted on it. (output divided by input) • Mechanical = Output Force Advantage Input Force
What is the mechanical advantage of a machine? You exert 10 N (input) of force on a can opener. The can opener exerts 30 N (output) of force on the can. What is the mechanical advantage? Mechanical = Output Force = 30 N Advantage Input Force 10 N Mechanical Advantage = 3
What is the efficiency of a machine? • The EFFICIENCY compares: –the work you put IN to –the work the machine puts OUT. • An IDEAL machine is 100% efficient. INPUT WORK = OUTPUT WORK • In the real world, some input work is always lost due to FRICTION between the moving parts of the machine.
What is the efficiency of a machine? EFFICIENCY = Output Work x 100% Input Work You mow the lawn with a rusty lawn mower. You do 50,000 J of work on the lawn mower but only 25,000 J go to cutting the lawn. What is the efficiency of the lawn mower?
What is the efficiency of a machine? You mow the lawn with a rusty lawn mower. You do 50,000 J of work on the lawn mower but only 25,000 J go to cutting the lawn. What is the efficiency of the lawn mower? EFFICIENCY = Output Work x 100% Input Work Efficiency = 25,000 J x 100% 50,000 J Efficiency = 50%
Try the rest of the practice problems on your own… Mechanical = Output Force Advantage Input Force EFFICIENCY = Output Work x 100% Input Work
The next slides go on the back of your foldable! Topic: Work and Force • Remember Science ROCKS!!! 
Evidence of Energy = when work has been done. • Work means: 1. Apply a force to an object over a distance. 2. Object moves in response to force. Remember Force = push or a pull Unbalanced force = movement Balanced force = no change in movement Spring Scale measures force and Newtons (N) are the units!
If something changes motion = it has energy! Cause Effect 1.Toy car at rest is pushed It moves = energy evidence =work 2.Fan is connect to a electric circuit It spins(moves)= energy evidence=work 3.Object is lifted It rises(moves) = energy evidence=work 4. A student pushes a wall The wall does NOT move = no work 5.A student stands wears a heavy bag The students continues to stand = no work You try: 6. A rocket accelerates through space 7. A book falls off the table 8. A girl sits on the bench