Simple Machines A machine is a device that makes work easier by changing the size or direction of the force. Machines make work easier because they allow the force to be applied over a greater distance, NOT because they increase the amount of work done! Mechanical Advantage is the number of times a machine multiplies the input force / effort. Most machines are made of one or more simple machines.

Lever A lever is a simple machine that has a bar that pivots at a fixed point, called a fulcrum. They are used to apply a force to a load.

Lever There are 3 classes of levers:

1st Class Lever ex. seesaw, scissors The Mechanical Advantage of a 1st class lever depends on where the fulcrum is - when the fulcrum is exactly in the middle, the MA = 1. When the fulcrum is closer to the load, the MA > 1. When the fulcrum is closer to the input force / effort, the MA < 1.

2nd Class Lever ex. wheelbarrow The Mechanical Advantage of a 2nd class lever is >1. The closer the load is to the fulcrum, the more the force is increased, and the greater the MA.

3rd Class Lever ex. hammer, stapler, arm The Mechanical advantage of a 3rd class lever is less than one because force is decreased. But, since the distance is increased for the output force / load, it does make work easier.

LEVER 1st Class Lever 2nd Class Lever 3rd Class Lever

Pulley A pulley is a simple machine that has a grooved wheel over which a rope, cable, or chain passes. A load is attached to one end of the rope, and an input force is applied to the other end.

Fixed Pulley A fixed pulley is attached to something that doesn’t move. The Mechanical Advantage of a fixed pulley = 1. So, even though the input and output force are the same, a pulley makes the job easier because the direction of the force changes.

Movable Pulley The pulley is attached to the object being moved. The Mechanical Advantage of a movable pulley is equal to 2. The direction of the force doesn’t change, but increases force and distance, which makes work easier.

Block and Tackle Made of a fixed and movable pulley together. The Mechanical Advantage of a Block and Tackle depends on the number of rope segments. It multiplies your input force by the number of rope segments, but you also have to pull the rope more to affect the load.

PULLEY Fixed Moveable Block & Pulley Pulley Tackle

Wheel and Axle ex. wheels, doorknob A wheel and axle is a simple machine made of 2 circular objects of different sizes. The wheel is the larger of the 2 objects.

Wheel and Axle When a small input force is applied to the wheel, the wheel turns through a circular distance. As the wheel turns, so does the axle. But, since the axle is smaller than the wheel, it rotates through a smaller distance, which makes the output force larger than the input force. The mechanical advantage of a wheel and axle is >1. MA = radius of wheel radius of axle

WHEEL & AXLE

Inclined Plane ex. ramp, slide, stairs An inclined plane is a simple machine that is a straight, slanted surface, which makes raising loads easier.

Inclined Plane The bigger the ratio of the plane’s length to height, the bigger the Mechanical Advantage. With an inclined plane, the same work is done on the load, but over a longer distance. MA = length height

INCLINED PLANE

ex. knife, doorstop, chisel Wedge ex. knife, doorstop, chisel A wedge is a simple machine that is made of 2 inclined planes that move, and is often used for cutting. Mechanical Advantage = length greatest thickness There is more MA when the wedge is longer and thinner!

WEDGE

ex. jar lid, screw, corkscrew A screw is a simple machine that is an inclined plane wrapped in a spiral around a cylinder. When the screw is turned, a small force is applied over the longer distance of the inclined plane of the screw. So, the screw applies a large force through the short distance.

ex. jar lid, screw, corkscrew  There is a greater Mechanical Advantage when there is a long spiral, and close threads on the screw.

SCREW

Compound Machines Compound Machine is a machine made of two or more simple machines. Example: Can opener the handle = second class lever the blade = wedge the knob you turn = wheel & axle

Compound Machine The mechanical efficiency of a compound machine is often low because more moving parts means more friction to overcome. Compound Machines Simple Machines

On the back of your notes, draw a Bubble Map (see example below) for all six simple machines. Describe the simple machine, draw a simple picture of it, and give an example. wheel and axle Simple Machines lever pulley screw inclined plane wedge

Rube Goldberg was an American cartoonist, sculptor, author, engineer, and inventor. Goldberg is best known for a series of popular cartoons he created depicting complex devices that perform simple tasks in indirect, convoluted ways – now known as Rube Goldberg machines.

Rube Goldberg The "Self-Operating Napkin" is activated when the soup spoon (A) is raised to mouth, pulling string (B) and thereby jerking ladle (C) which throws cracker (D) past parrot (E). Parrot jumps after cracker and perch (F) tilts, upsetting seeds (G) into pail (H). Extra weight in pail pulls cord (I), which opens and lights automatic cigar lighter (J), setting off skyrocket (K) which causes sickle (L) to cut string (M) and allow the pendulum with the attached napkin to swing back and forth, thereby wiping chin.

Rube Goldberg Open window (A) and fly kite (B). String (C) lifts small door (D) allowing moths (E) to escape and eat red flannel shirt (F). As weight of shirt becomes less, shoe (G) steps on switch (H) which heats electric iron (I) and burns hole in pants (J). Smoke (K) enters hole in tree (L), smoking out opossum (M) which jumps into basket (N), pulling rope (O) and lifting cage (P), allowing woodpecker (Q) to chew wood from pencil (R), exposing lead. Emergency knife (S) is always handy to sharpen the pencil in case opossum or the woodpecker gets sick and can't work.

Rube Goldberg Design your own “Rube Goldberg” machine. The machine should be labeled with its purpose, as well as the parts and their function. I should be able to follow along the description to see what the machine’s purpose is. Be creative!!