Agenda: Extra Credit: Make a pic collage, pic grid, photo grid, etc showing me using at least 5 simple machines and post it on Edmodo!

Do this: On page 23 write this:•Machines make work easier by changing 3 things about the FORCE you exert to do work:

AMOUNTAMOUNT OF FORCE OF FORCE you exert you exert DISTANCEDISTANCE over which you exert over which you exert forceforce DIRECTIONDIRECTION in which you exert force in which you exert force

Standard:Demonstrate the effect of simple machines on workWhat am I learning today?What are the 6 types of simple machines?

How will I know that I learned it?I will give examples of the 6 different kinds of simple machines

Simple Machines(Making work easier…phew!)

What are MACHINES?• Most people think of complex, technical, Most people think of complex, technical,

or electronic gadgets with motors…, but or electronic gadgets with motors…, but machines can be much SIMPLER. machines can be much SIMPLER.

• A machine is any device that lets you do A machine is any device that lets you do WORKWORK in an in an EASIEREASIER or or BETTERBETTER way way..

• Basically: Basically: Simple machines make work Simple machines make work EASIER.EASIER.

How do machines do work?• Machines make work easier by

changing 3 things about the FORCE you exert to do work: AMOUNTAMOUNT OF FORCE OF FORCE you exert you exert DISTANCEDISTANCE over which you exert over which you exert forceforce DIRECTIONDIRECTION in which you exert force in which you exert force

What are SIMPLE MACHINES?• There are only 6 basic simple

machines that make work easier:

• Inclined PlaneInclined Plane• WedgeWedge• ScrewScrew• LeverLever• Wheel & AxleWheel & Axle• PulleyPulley

WORK & SIMPLE MACHINES• Simple machines Simple machines DON’TDON’T change change

the amount of the amount of WORKWORK done! done!(They change the size, distance (They change the size, distance or direction of your FORCE!)or direction of your FORCE!)

WORK INWORK IN = = WORK OUTWORK OUT**

(*usually machines lose a bit of (*usually machines lose a bit of work due to work due to FRICTIONFRICTION…)…)

Set up your Simple Machines foldable

Simple Machines Foldable• On the cover, write the name and On the cover, write the name and

draw a picture of the simple draw a picture of the simple machine.machine.

• Behind the flap, give 2-3 Behind the flap, give 2-3 examples.examples.

• Write the definition inside.Write the definition inside.

Machines make work easier by Machines make work easier by changing 3 things about the FORCE: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 Machines make work easier by changing 3 things about the FORCEchanging 3 things about the FORCE:

• The amount of force(eg. A ramp (inclined plane) lets you

lift a heavy object with LESS force)

Machines make work easier by Machines make work easier by changing 3 things about the FORCE: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 Machines make work easier by changing 3 things about the FORCE: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.

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

How do pulleys make work easier??

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

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

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 ForceOutput Force

WEDGE: Examples & Uses

• Ax, Knife, etc.• Zippers

• Used in all cutting machines (to split materials apart)

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

Glue the foldable on page 24

Simple Machine Review!

COMPOUND MACHINES• Compound Machines – are made of Compound Machines – are made of combinationscombinations of of

two or more two or more simple machinessimple machines. . • For example, a simple can opener is a combination of

3 simple machines: – Lever – Wheel & axle – Wedge

What is the mechanical mechanical advantage advantage of a machine? You exert You exert 10 N10 N (input) of force on a (input) of force on a

can opener. The can opener exerts can opener. The can opener exerts 30 30 NN (output) of force on the can. What (output) of force on the can. What is the mechanical advantage?is the mechanical advantage?

Mechanical = Mechanical = Output ForceOutput Force = = 30 N30 NAdvantageAdvantage Input Force 10 N Input Force 10 NMechanical Advantage = 3Mechanical Advantage = 3

What is the efficiency of a machine?

• The EFFICIENCY compares: The EFFICIENCY compares: – the the workwork you put you put ININ to to – the the workwork the machine puts the machine puts OUTOUT..

• An IDEAL machine is 100% efficient.An IDEAL machine is 100% efficient. INPUT WORK = OUTPUT WORKINPUT WORK = OUTPUT WORK

• In the real world, some input work is In the real world, some input work is always lost due to always lost due to FRICTIONFRICTION between between the moving parts of the machine.the moving parts of the machine.

What is the efficiencyefficiency of a machine?

EFFICIENCY = EFFICIENCY = Output WorkOutput Work x 100% x 100% Input WorkInput Work

You mow the lawn with a rusty lawn You mow the lawn with a rusty lawn mower. You do 50,000 J of work on mower. You do 50,000 J of work on the lawn mower but only 25,000 J the lawn mower but only 25,000 J go to cutting the lawn. What is the go to cutting the lawn. What is the efficiency of the lawn mower?efficiency of the lawn mower?

What is the efficiencyefficiency of a machine?

You mow the lawn with a rusty lawn mower. You mow the lawn with a rusty lawn mower. You do 50,000 J of work on the lawn mower You do 50,000 J of work on the lawn mower but only 25,000 J go to cutting the lawn. but only 25,000 J go to cutting the lawn. What is the efficiency of the lawn mower?What is the efficiency of the lawn mower?

EFFICIENCY = EFFICIENCY = Output WorkOutput Work x 100% x 100% Input Work Input Work

Efficiency = Efficiency = 25,000 J25,000 J x 100% x 100%50,000 J50,000 J

Efficiency = 50%Efficiency = 50%

Try the rest of the practice problems on your own…

Mechanical = Mechanical = Output ForceOutput Force AdvantageAdvantage Input Force Input Force

EFFICIENCY = EFFICIENCY = Output WorkOutput Work x 100% x 100% Input Work Input Work

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 pullUnbalanced force = movementBalanced force = no change in movement

Spring Scale measures force and Newtons (N) are the units!

If something changes motion = it has energy!

Cause Effect1.Toy car at rest is pushed It moves = energy evidence =work2.Fan is connect to a electric circuit It spins(moves)= energy evidence=work3.Object is lifted It rises(moves) = energy evidence=work

4. A student pushes a wall The wall does NOT move = no work5.A student stands wears a heavy bag The students continues to stand = no work

You try:6. A rocket accelerates through space7. A book falls off the table8. A girl sits on the bench