Simple Machines Mechanical Advantage WORK 1 Efficiency Effort Force

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Presentation transcript:

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

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!

How Machines Work You do WORK on the machine And The machine does WORK on an object Your WORK=Fxd The machine’s WORK=Fxd The amount of work is EQUAL!

A machine can make work easier in two ways: Machines only make work easier…HOW? 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 …is the number of times the machine multiplies the effort force (your force)

Ideal vs Actual Mechanical Advantage 7.1 Ideal vs Actual Mechanical Advantage IMA AMA IMA-WHAT ACTUALLY happened!! Why is this different from IMA? FRICTION…. Converts some energy in into thermal energy, so less USEFUL energy out.

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.

Get a calculator Work on Vocab (p.10)

Working Together (you and the machine)

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. NEVER OVER 100%

According To “The Law of Conservation of Energy” Can this exist? 10 Ideal machine Efficiency is=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 Fulcrum 12 (Fe) Effort Force LOAD (Fr) Resistance Force The force the person applies to the machine Place where a lever pivots The distance the machine moves the load Fulcrum (Fe) Effort Force (dr) Resistance Distance Effort Arm Resistance Arm LOAD (de) Effort Distance (Fr) Resistance Force The distance the person moves the machine The force the machine applies to the load

Based on the position of the fulcrum 13 Levers There are 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 2nd Class: The resistance force is between the effort force and the fulcrum. Wheelbarrow Nutcrackers 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 10 cm 5 cm 5 cm LOAD 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 “Give me a place to stand and with a lever I will move the whole world.” -Archimedes

MA of Levers Problems Example #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?

MA of Levers Problems Example #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?

Example #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?

From study packet…page 2 1) A construction worker uses a board and log as a lever to lift a heavy rock. If the input arm is 3 meters long and the output arm is 0.75 meters long, what is the mechanical advantage of the lever?

From study packet…page 2 2) Marshall wants to remove a tree stump from the ground. To do this, he puts one end of a long beam under the stump and puts all of his weight on the other end. His weight is just enough to lift the stump. The stump weighs 400 N. Marshall weighs 250 N. What is the mechanical advantage of the lever Marshall is using?

From study packet…page 2 3) A lever and fulcrum are used to raise a heavy rock, which has a weight of 445 N. If the lever has a mechanical advantage of 9.50, what must the input force on the lever be in order to just begin lifting the rock?

From study packet…page 3 4) Susan and Jake take Susan’s car for a drive and get stuck in the mud. The back of Susan’s car weighs 900 N. They applied 700 N of force to the tree branch lever. What is the mechanical advantage of the tree branch?

From study packet…page 3 5) Three of your friends are all sitting on one end of a seesaw. The combined weight is 275 N. The length from the fulcrum to your friends is 2.5 m. The rest of the seesaw (from the fulcrum to you) is 4.5 m. What is the MA? B) What effort force is needed to lift your friends?

From study packet…page 3 6) How can you increase the mechanical advantage of a lever?

18 REVIEW Position of Fulcrum

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 Effort Force Test question: Resistance force is equal to the ___________ of the __________. 100N Resistance Force

Mechanical Advantage of Pulleys 24 MA =2 Effort Force 100N Resistance Force

Mechanical Advantage of Pulleys 25 MA =4 Effort Force 100N Resistance Force

Example problem 1: A simple pulley system uses a 40N effort force to move a 80N load. What is the Mechanical Advantage of the pulley?

Example Problem 2: To lift a load 5cm with a pulley system, 15cm of string had to be pulled. What is the mechanical advantage?

A pulley is used to raise a heavy crate A pulley is used to raise a heavy crate. The pulley is such that an input force of 223 N is needed to provide an output force of 1784 N. What is the mechanical advantage of this pulley?

A complex arrangement of pulleys forms what is called the block in a block and tackle. The rope used to lift the pulleys and the load is the tackle. A block and tackle is used to lift a truck engine, which has a weight of nearly 7406 N. The force required to lift this weight using the block and tackle is 308.6 N. What is the mechanical advantage of the block and tackle?

A block and tackle with a mechanical advantage of 48 is used to lift a piano 11 m to the third floor of a building. Although the arrangement of pulleys in the block and tackle makes it easy to lift the piano, it takes a long time because of the length of rope that must be pulled to lift the piano a small amount. What is this length, or input distance, of the rope that must be pulled?

Marc is asked to raise a flag at the Remembrance Day ceremonies at his school. If the effort force to raise the flag is 50 N and the load force the flag plus the rope is 50 N what is the mechanical advantage of the pulley on the flagpole?

26

28.a Inclined Planes

28.b Inclined Plane A sloping surface 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

Questions: Since doing a task with or without a machine requires the same amount of work, why use machines? Answer: They give you a mechanical advantage. You get your force multiplied.

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!

Why do you think you see these type of door knobs in handicap accessible areas?

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: Bolts, Spiral Staircase, Parking Deck

33 The closer together the threads are, the longer the inclined plane is relative to the length of the screw or bolt, so the greater its mechanical advantage. Therefore, if the threads are closer together, you need to apply less force to penetrate the wood or other object.

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

Quick Review Look at your “19cm lever” on pg 7. How much work did you do? How much work did the lever do? If you used a lever with an effort arm 20cm and a resistance arm of 10cm to lift a box with a weight of 700N, what would be the mechanical advantage of the lever? If you used the pulley in the picture to lift a box with a weight of 500N, about how much force would you need to apply to the pulley?

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

TedEd: The mighty mathematics of the lever What does he say at 1:20 that is wrong?

Simple Machines: Pulleys (12:52)

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Simple Machines