Simple Machines W O R K M e c h a n i c a l A d v a n t a g e Force Effort E f f i c i e n c y 1 Sound
Goals Analyze the simple machines qualitatively and quantitatively in terms of force, distance, work and mechanical advantage Be able to calculate mechanical advantage Be able to calculate amount of work done by a simple machine Explain the different types of simple machines. 2 What do I need to know?
Work TTTTransfer of Energy from one place to another. AAAApplying a force over a certain distance. CCCCalculating Work: WWWWork= Force x distance WWWW = f x d F L A S H B A C K 3
6 types of simple machines 4 clip
What is a machine? 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! 5
M ultiply the force you apply. AAAA Car Jack C hange the direction of the force. BBBBlinds A machine can make work easier in two ways: 6
Mechanical Advantage Number of times the machine multiplies the effort force (The force you apply to it) 7.1 CLIP
Ideal vs Actual Mechanical Advantage IMA WHAT ACTUALLY happened!! Why is this different from IMA? 7.1
Machines are a “give and take relationship.” If you get your force multiplied, then you must go a greater distance. Watch for this in all Simple machines : 8
Types of Machines 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? 11
Levers Resistance ArmEffort Arm Resistance Force Resistance Distance Fulcrum 12 Effort Force Effort Distance LOAD
Levers There are three types of Levers Based on the position of the fulcrum 13
Levers The fulcrum is between the resistance force and the effort force. 1st Class: 1st Class: Crowbars, pliers, scissors, seesaw The closer the fulcrum to the resistance force, the more the lever multiplies the force. 14
Levers 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 15
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) 16
17 Mechanical Advantage of Levers As the length of the effort arm increases, the MA of the lever increases. Effort arm Resistanc e arm 5/5=1 10/5=2 20/5=4 3 Ways
Mechanical Advantage of Levers You can also use the Mechanical Advantage Formulas: IMA Ideal MA AMA Actual MA
REVIEW Position of Fulcrum 18
MA of Levers Problems 1.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? 2.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? 3.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?
Efficiency of a Machine NEVER OVER 100% 90 J. 100 J A measure (%) of how much work put into a machine is actually changed to useful work put out by the machine. 9
Ideal machine D o e s n o t e x i s t. Efficiency =100% FRICTION According To “The Law of Conservation of Energy” Can this exist? 10
Pulleys 19
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? Pulleys 1.Multiply the effort force 2.change the direction of the force 20
Pulleys Two types of Pulleys: 1.Fixed pulley –A pulley that is attached to something –Only changes the direction of the force 2.Movable pulley –The pulley is free to move ***Block and Tackle*** Combination of both types of pulleys 21
Mechanical Advantage of Pulleys Effort Force resistance Force M A = 1 10 N Only changes the direction of the force 22
Mechanical Advantage of Pulleys M A = 2 23
Mechanical Advantage of Pulleys M A = 2 24
Mechanical Advantage of Pulleys M A = 4 25
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Inclined Plane A sloping surface that that reduces the amount of force required to raise and object. Effort Distance (l) R e s i s t a n c e D i s t a n c e ( h ) 28
Mechanical Advantage of Inclined Planes 29 Effort Distance (l)R e s i s t a n c e D i s t a n c e ( h )
Mechanical Advantage of Inclined Planes 30
Animation Starter on page 6 in packet…click
Wheel and Axle Consisting of two wheels of different sizes that rotate together The effort force is applied to the larger wheel 31.a
Ideal Mechanical Advantage = Radius of wheel Of wheel and axle Radius of axle Gears are wheels with teeth. The effort force is applied to the larger wheel 31.b
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? 31.c IMA = 10 This means with each turn of the axle, you get 10 times the distance. Those big wheels really help! Ideal Mechanical Advantage = Radius of wheel Of wheel and axel Radius of axel
Screw An inclined plane wrapped around a cylinder The inclined plane lets the screw slide into the wood. 32 Examples: Bolt, Spiral Staircase
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Wedge An inclined plane with one or two sloping sides. Changes the direction of the effort force. Effort Force Resistance force 34 Examples: Axe, Zipper, Knife
35 Review Clip
36 Rube Goldburg Keep You From Forgetting To Mail Your Wife's Letter
CLIP 37 Simplified Pencil Sharpener
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A 25 B 10 C 5 D 4 A lever is used to lift a box. The mechanical advantage of the lever is 50 cm 10 cm OR It took only 200 N of force to lift a 1000N object, therefore the machine multiplied the force 5 times! 39
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 = W out 88 J
Which of the following is an example of a compound machine? A bicycle B crowbar C doorknob D ramp 41