Bell ringer If the input force is bigger than the output force, then the input distance is __________ than the output distance. If the output force is bigger than the input force, then the input distance is __________ than the output distance. If the input force is smaller than the output force, then the input distance is __________ than the output distance. If the output distance is bigger than the input distance, then the input force is __________ than the output force. 4/14/2017

Simple Machines Physical Science 4/14/2017

Types of Machines: Simple machines are simple tools used to make work easier. Compound machines have two or more simple machines working together to make work easier. 4/14/2017

Simple Machines Simple Machine  Does work with one movement... There are six simple machines: (1) lever (2) pulley (3) inclined plane (4) wedge (5) screw (6) wheel and axle 4/14/2017

Lever Lever  Bar that pivots around fixed point. Fixed point = fulcrum 4/14/2017

Three Classes of Levers IF F OF 1st Class Lever F OF IF 2nd Class Lever F IF OF 3rd Class Lever IF = Input force F = Fulcrum (pivot point) OF = Output force 4/14/2017

Three Classes of Levers 1st class lever Change direction of force Examples: scissors, seesaw IF F OF Fulcrum is always between input force and output force in a first-class lever. 4/14/2017

Three Classes of Levers 2nd class lever Does not change direction of force Examples: wheelbarrow, paper cutter F OF IF 4/14/2017

Three Classes of Levers 3rd class lever Examples: baseball bat, arm, golf club, tennis racket F E R 4/14/2017

Mechanical Advantage and Levers 2 arms of lever: The input arm is the distance between the input force and the fulcrum. The output arm is the distance between the output force and the fulcrum. If input arm > output arm, IMA > 1 If input arm = output arm, IMA = 1 If input arm < output arm, IMA < 1 4/14/2017

Mechanical Advantage and Levers Output Arm Input Arm Output Arm Input Arm Input Arm Output Arm IMA > 1 IMA = 1 IMA < 1 4/14/2017

Which type of lever? 4/14/2017

Which type of lever? 3rd Class Lever 4/14/2017

Which type of lever? 4/14/2017

Which type of lever? 2rd Class Lever 4/14/2017

Which type of lever? 4/14/2017

Which type of lever? 1rd Class Lever 4/14/2017

Which type of lever? 4/14/2017

Which type of lever? 3rd Class Lever 4/14/2017

Which type of lever? 4/14/2017

Which type of lever? 1rd Class Lever 4/14/2017

A Crowbar Is A First-Class Lever A crowbar is a first-class lever. It changes the direction of the applied force. Because it has a long effort arm and a short resistance arm, it also greatly multiplies the force. 4/14/2017

Pulley Pulley  a chain, belt, or rope wrapped around a wheel… Can change direction or size of Force. 4/14/2017

Pulley Fixed pulley  one that is attached to a ceiling, wall, etc. Only changes the direction of the effort force MA of a single fixed pulley is always one. Movable pulley  pulley hung on a rope that it moves with the effort force… Can multiply the effort force, but cannot change the direction… MA for movable pulley is always greater than one. 4/14/2017

A Fixed Pulley Changes direction of force. MA = 1 Use just as much force to lift the box as you would by picking it up directly. 100 lbs 100 lbs 4/14/2017

A Moveable Pulley Does not change direction of force. MA = 2 50 lbs Does not change direction of force. MA = 2 Allows you to lift a 100-pound weight with only 50 pounds of force, but… 2 feet 1 foot 100 lbs 4/14/2017

Pulley You can combine fixed and movable pulleys to increase the MA even more… This is a pulley system… 4/14/2017

Pulley Systems IMA = 1 IMApulley = strands of rope that support the mass. IMA = 4 IMA = 2 4/14/2017

Inclined Plane Inclined plane  slanted surface used to raise obj. A ramp. IMA of ramp > 1 4/14/2017

Inclined Plane Height Length of plane 4/14/2017

Without An Inclined Plane Force 4/14/2017

With An Inclined Plane (And Rollers) Force 4/14/2017

Wedge Wedge  a V-shaped object whose sides are two inclined planes sloped toward each other. Examples include: knife blade razor blade axe head a door stopper Sharpening increases AMA... 4/14/2017

Wedges Compare the force needed to split a piece of wood using each axe head. Which axe head has the higher MA? 10 20 30 40 50 60 Newtons 10 20 30 40 50 60 Newtons The sharper axe head has the higher Mechanical Advantage. It takes less force to do the same amount of work. 4/14/2017

Screw Screw  Inclined plane wrapped around cylinder. Examples: Closer threads  larger AMA... Examples: Hardware screw Light bulb base Jar lid 4/14/2017

Without Screws Lifting this gate manually is hard work; it requires lots of force. 4/14/2017

With Screws Screws change rotational motion into straight-line motion. It takes a lot less force to lift the gate, but it takes a longer time. 4/14/2017

Wheel and Axle Wheel and axle  a lever that rotates in a circle… Made of two wheels of different sizes… Axle is a smaller wheel… Larger wheel turns about the smaller axle… Wheel moves through a greater distance; Effort force applied to the wheel is multiplied at the axle… Examples: Bicycles, Ferris wheels, water wheels, gears… 4/14/2017

Wheel and Axle The wheel and axle makes it easier to raise the crate. Any force applied to the large wheel is multiplied in the smaller axle. But the wheel must be turned much farther to lift the crate. 4/14/2017

Gears A gear is a modified wheel and axle. Gears can change the size or direction of a force. 4/14/2017

Compound Machines Compound machines  combination of two or more simple machines… ***Remember…simple or compound, you can get no more work out of a machine than you put into it!! Machines cannot multiply work!!! An automobile engine is a compound machine made of many simple machines, including pulleys, wheels and axles, levers, and screws. 4/14/2017