Simple Machines Mechanical Advantage WORK 1 Efficiency Effort Force Sound Efficiency Effort Mechanical Advantage WORK Force

2 Goals What do I need to know? 1.Analyze the simple machines qualitatively and quantitatively in terms of force, distance, work and mechanical advantage 2. Explain the different types of simple machines. 3. Be able to calculate amount of work done by a simple machine 4.Be able to calculate mechanical advantage 5. Use mathematics & computational thinking to identify the relationships between work, mechanical advantage, and simple machines

Working Together

Work FLASH BACK Transfer of Energy from one place to another. 3 Work FLASH BACK Transfer of Energy from one place to another. Applying a force over a certain distance. Calculating Work: Work= Force x distance W = f x d

6 types of simple machines 4 6 types of simple machines clip

What is a machine? -a machine that does work with only one movement. 5 A device that makes work easier. What is a simple machine? -a machine that does work with only one movement. You still do the same amt of work —it’s just easier!

A machine can make work easier in two ways: 6 A machine can make work easier in two ways: Multiply the force you apply. A Car Jack Change the direction of the force. Blinds

7.1 Mechanical Advantage CLIP Number of times the machine multiplies the effort force (The force you apply to it)

Ideal vs Actual Mechanical Advantage 7.1 Ideal vs Actual Mechanical Advantage IMA- The mechanical advantage of a machine in the absence of friction WHAT ACTUALLY happened!! Why is this different from IMA? AMA- The mechanical advantage of a machine in the presence of friction

Watch for this in all Simple machines: 8 Watch for this in all Simple machines: Machines are a “give and take relationship.” If you get your force multiplied, then you must go a greater distance.

Efficiency of a Machine 9 A measure (%) of how much work put into a machine is actually changed to useful work put out by the machine. 90 J . 100 J NEVER OVER 100%

According To “The Law of Conservation of Energy” Can this exist? 10 Ideal machine Efficiency =100% According To “The Law of Conservation of Energy” Can this exist? Does not exist. FRICTION

Types of Machines Levers 11 Types of Machines Levers A lever is a bar that is free to pivot, or turn about a fixed point. How can we use levers?

Levers 12 Fulcrum Resistance Distance Effort Distance Effort Arm LOAD Effort Arm Resistance Arm Resistance Force Effort Force

Levers There are three types of Levers 13 Levers There are three types of Levers Based on the position of the fulcrum

The fulcrum is between the resistance force and the effort force. 14 Levers 1st Class: Crowbars, pliers, scissors, seesaw The fulcrum is between the resistance force and the effort force. The closer the fulcrum to the resistance force, the more the lever multiplies the force.

Levers 15 Wheelbarrow Nutcrackers Crowbar (forcing two objects apart) 2nd Class: The resistance force is between the effort force and the fulcrum. Wheelbarrow Nutcrackers Crowbar (forcing two objects apart) The handle of a pair of nail clippers

16 3rd Class: the effort force is between the resistance force and the fulcrum. Levers Garden Hoe Your arm Catapult Fishing rod Tongs (double lever) (where hinged at one end)

Mechanical Advantage of Levers 17 Mechanical Advantage of Levers 3 Ways 5/5=1 10/5=2 20/5=4 Effort arm Resistance arm As the length of the effort arm increases, the MA of the lever increases.

Mechanical Advantage of Levers You can also use the Mechanical Advantage Formulas: IMA Ideal MA AMA Actual MA

18 REVIEW Position of Fulcrum

MA of Levers Problems To pull apart two pieces of wood, you apply a force of 50 N to a lever. The lever then applies a force of 640 N to the wood. What is the mechanical advantage of the lever? A lever and fulcrum are used to raise a heavy rock, which has a weight of 350 N. If the lever has a mechanical advantage of 9, what must the input force on the lever be in order to just begin lifting the rock? A construction worker uses a board and log as a lever to lift a heavy rock. If the input arm is 6 meters long and the output arm is 1.2 meters long, what is the mechanical advantage of the lever?

19 Pulleys

Pulleys Multiply the effort force change the direction of the force 20 What is a pulley? A pulley is a grooved wheel with a rope or chain running along the groove. What can a pulley be used for? Multiply the effort force change the direction of the force

Pulleys 21 Two types of Pulleys: Fixed pulley Movable pulley A pulley that is attached to something Only changes the direction of the force Movable pulley The pulley is free to move ***Block and Tackle*** Combination of both types of pulleys

Mechanical Advantage of Pulleys 22 Only changes the direction of the force MA =1 10 N resistance Force Effort Force 10 N

Mechanical Advantage of Pulleys 23 MA =2

Mechanical Advantage of Pulleys 24 MA =2

Mechanical Advantage of Pulleys 25 MA =4

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28 Inclined Plane A sloping surface that that reduces the amount of force required to raise and object. Resistance Distance (h) Effort Distance (l)

Mechanical Advantage of Inclined Planes 29 Effort Distance (l) Resistance Distance (h)

Mechanical Advantage of Inclined Planes 30

Animation Starter on page 6 in packet…click

31.a Wheel and Axle Consisting of two wheels of different sizes that rotate together The effort force is applied to the larger wheel

The effort force is applied to the larger wheel 31.b Ideal Mechanical Advantage = Radius of wheel     Of wheel and axle        Radius of axle The effort force is applied to the larger wheel Gears are wheels with teeth.

31.c One day you made a mousetrap cars. The car has the following measurements for their wheels:  the radius axle (the small wheel) measured only 1 cm.  The radius of the larger wheel (the one that touched the pavement) measured a whopping 10cm.  What was the mechanical advantage of these wheels? Ideal Mechanical Advantage = Radius of wheel     Of wheel and axel        Radius of axel IMA = 10 This means with each turn of the axle, you get 10 times the distance.  Those big wheels really help!

Screw An inclined plane wrapped around a cylinder 32 Screw An inclined plane wrapped around a cylinder The inclined plane lets the screw slide into the wood. Examples: Bolt, Spiral Staircase

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Wedge 34 An inclined plane with one or two sloping sides. Changes the direction of the effort force. Examples: Axe, Zipper, Knife Effort Force Resistance force

Review Clip 35

36 Rube Goldburg Keep You From Forgetting To Mail Your Wife's Letter

37 Simplified Pencil Sharpener CLIP

EOCT QUESTIONS 38

A lever is used to lift a box. The mechanical advantage of the lever is 39 It took only 200 N of force to lift a 1000N object, therefore the machine multiplied the force 5 times! A 25 B 10 C 5 D 4 OR 50 cm 10 cm

40 What is the amount of useful work output of a 25% efficient bicycle if the amount of work input is 88 N-m? A 2200 N-m B 113 N-m C 63 N-m D 22 N-m Wout .25 = 88 J

Which of the following is an example of 41 Which of the following is an example of a compound machine? A bicycle B crowbar C doorknob D ramp

Simple Machines