Who can lift me with 1 hand?

Simple machines help make a job easier by: Changing how much FORCE is NEEDED or the Direction of the Force Archimedes once said: give me a lever long enough and a place to stand and I will move the earth

Machines are all just combinations of 4 basic type: Lever Pulley Wheel & Axle Inclined Plane

The force you apply to the machine Effort Force, FE The force you apply to the machine FR FE Resistance Force, FR : The force actually applied to the resistance (usually equal to the weight of an object)

Distance of effort (dE) By pushing on the lever you do WORK on it FE FR Distance of effort (dE) Work input = FEdE

Distance of resistance (dR) AND WORK COMES OUT Distance of resistance (dR) FE FR Work Ouput = FRdR

FRdR = FEdE FR dE if an ideal machine work out = work in Compare the Work Out to the work input FRdR = FEdE work out = work in The lever used to lift me reduced the Force needed to lift me but not the WORK!!! FR FE dE dR if an ideal machine

Work Output = Work Input If no energy (or work) is lost to friction then…. Work out FE FR Work in Work Output = Work Input

Work Output = Work Input (For an ideal machine – no friction) This is a best case & You can never get more work out than the work put in!!!! That would be like making energy

Simple machines magnify the input force but at a cost….

FR MA = FE FR FE Mechanical Advantage This is how much your force gets multiplied by a machine, or by how much the required force to do a job is reduced If MA >1 then… If MA < 1 then…

What’s is the MA? 10 N 100 N

What’s is the MA? 200 N 100 N

Is the lever ideal (frictionless)? The effort side of a lever is pushed down with a force of 90 N for 1.8 m. This lifted a box weighing 270 N up .6 m. What is the work input? What is the work output? What is the MA? Is the lever ideal (frictionless)? FE FR

One side of a lever is pushed down by a person with a force of 50 N and a 200 N object is lifted. If the person pushes the lever down 1 m, how far does the other side move up? (if the lever is frictionless) FE FR

If an ideal lever is such that when a person pushes their side down If an ideal lever is such that when a person pushes their side down .8 m, it lifts a load on the other side up .2 m. If the load weighs 100 N, how hard does the person need to push? FE FR

If there is no friction then the Mechanical Advantage can be determined by looking at the distances What is the ideal Mechanical Advantage here? 6 m 2 m

IDEAL MECHANICAL ADVANTAGE Because we ratio of the distances is related to how much the Effort Force gets magnified. IDEAL MECHANICAL ADVANTAGE dE IMA = dR This is the MA if there is no friction

What is the IMA? .75 m .25 m

Where should the fulcrum (pivot point) be placed to reduce the applied force?

What happens it the fulcrum is placed in the middle?

500 N 100 N What happens to the applied force if the fulcrum is moved closer to it?

Book Problems Read pages 111-116 Page 120 14, 15,16,17, 18,19 28 –Find the MA, IMA TOO 29 – only part a.)

Type 1 TYPES OF LEVERS Resistance Effort The difference is the relative locations of the effort, fulcrum, and resistance Type 2 Resistance Effort Type 3 Effort

How does the direction of applied force vary? Type 1 TYPES OF LEVERS Resistance Effort Type 2 How does the direction of applied force vary? Resistance Effort Type 3 Effort Resistance

Compared to the resistance can each type make the applied force Effort Compared to the resistance can each type make the applied force Less, more, or both? Type 2 Resistance Effort Type 3 Effort Resistance

Type 1 Type 2 Type 3 Resistance Effort Resistance Effort Effort

Which type of lever is this? input output

Which type of lever is this? input output

ID the levers input output

ID the levers output input

Pulleys They range from simple To complex

Simple Pulley is just a round wheel with an axle in the middle and a groove to keep a rope on it

A Simple Pulley Direction of Forces Which moves more? Output force Input force 100 N

What is the MA of this type of machine? The force and resistance must move the same amount so the FE = FR

A pulley like this acts like a Type 1 Lever with the fulcrum in the middle Forces are reversed with equal magnitudes 100 N 100 N 100 N

Will the input Force be 100 N? Output force 100 N

The Effort force is ½ the Resistance

To lift the resistance 1 m 2 m of rope must be pulled 1 m

What is the MA of this type of machine?

Typically the number of strings attached to the load is the MA

A pulley like this acts like a Type 2 lever with the resistance in the middle

Pulleys can be combined to change direction and magnify the effort force

But what is the tradeoff here? The Possibilities are Endless!

Simple machines WS

Simple machines lab

Go over simple machines ws

ID the levers

How much your force is multiplied FR How much your force is multiplied MA = FE If an IDEAL pulley has an MA of 4, how much rope do you need to pull to lift the resistance 2 m? 4 times as much or 8 m

NO work or energy is “lost” as For an IDEAL Machine WorkOUT = WorkIN HEAT NO work or energy is “lost” as If there is no FRICTION

Input work output work heat Realistically there is always some friction 10 J 8 J Input work output work 2 J heat So in the real world you never get out as useful work what you put in

Efficiency is what % of the input work comes out at useful work Work out 100% Efficiency = Work in

If a machine is 50% efficient Work out 50 J 50 % = 100 J Work in You have to put 100 J of work in to get 50 J out

For an ideal machine Work Output = Work Input If a 100 J is put in then 100 J comes out 100 J Efficiency = 100 J Efficiency = 100%

A frictionless lever below FE FR dR dE Work in = Work out Efficiency = 100%

To overcome friction extra force must be applied to do the same thing FE FR dR dE

A lever is such that if the effort side is pushed down 2 m with a force of 3 N, a 4 N load is lifted 1 m. What is the efficiency of the lever?

Using a machine which is 20% efficient, how much work will have to be applied to a machine to lift a 10 N weight up 2 m?

To overcome friction extra force must be applied to do the same thing FE FR dR dE

FE What changed because of friction FR FE dE dR To overcome friction extra force must be applied to do the same thing FE FR dR dE What changed because of friction FE FR FE dE dR

FE FE How does that affect FR MA = FR FE dE dR To overcome friction extra force must be applied to do the same thing FE FR dR dE How does that affect FR MA MA = FE FE FR FE dE dR

FE How does that affect dE IMA = dR FR FE dE dR NO CHANGE To overcome friction extra force must be applied to do the same thing FE FR dR dE How does that affect dE IMA = FE dR FR FE dE dR NO CHANGE

FE Work in How does that affect Work in = FE dE FR FE dE dR To overcome friction extra force must be applied to do the same thing FE FR dR dE How does that affect Work in = FE dE FE Work in FR FE dE dR

FE How does that affect Work out = FR dR FR FE dE dR NO CHANGE To overcome friction extra force must be applied to do the same thing FE FR dR dE How does that affect FE Work out = FR dR FR FE dE dR NO CHANGE Work out

FE Work in How does that affect FR FE dE dR Work out Efficiency = To overcome friction extra force must be applied to do the same thing FE FR dR dE How does that affect FE FR FE dE dR Work out Efficiency Efficiency = Work in

SHOW WORK WHERE APPLICABLE Book Problems 119-121 Page 120:, 29 b, 39, 42, 43, 45, 47 X.) How much input work will be needed to do 300 J of output work using a machine which is 35% efficient? How much work is lost as heat? Q.) In lifting a 1.5 kg mass up 2.0 m, the effort side of a lever is pushed down with 10.0 N of force for 4.0 m. What is the efficiency of the lever?