Simple Machines Discussion

Simple Machines A simple machine has

few or no moving parts. Simple machines make

work easier. With or without a

simple machine the work is the same.

Also when simple machines are combined they can make complicated bigger machines.

Simple Machines Wheels and Axles

A wheel axle is a simple machine made of two circular or cylindrical objects that are fastened together and that rotate about a common axis.

The object with larger diameter is the wheel. The object with the shorter diameter is the axle.

Simple Machines Wheels and Axles

With a screwdriver the handle is the wheel and the shaft is the axle

Every time you turn a door knob, you are using a wheel and axle. The knob is the wheel and the shaft is the axle.

The steering wheel of a car is also another example.

Simple Machines Pulleys A Pulley is a grooved

wheel with a rope, or a chain, or even a steel cable wrapped around it.

You use a pulley by pulling on the rope. As a result, you can change the amount and direction of your input force.

Simple Machines Pulleys Garage Doors

are one of the most common pulley systems.

Elevators also use the pulley system.

Simple Machines Inclined Planes

An inclined plane is a flat surface that is higher on one end

Inclined planes make the work of moving things easier.

Simple Machines Inclined Planes

Inclined planes are always used on moving trucks or trucks that have to carry a lot of weight.

Some roads also are slanted like inclined planes.

Simple Machines-Wedges A wedge is a device

that is thick at one end and tapers to a thin edge at the other end.

It might be helpful to think of a wedge as an inclined plane (or two inclined planes back to back) that can move.

Simple Machines-Wedges Examples of

wedges are knifes, axes, and zippers.

Sometimes lumberjacks will place wedges in tree’s when they are cutting them down it makes it easier.

Simple Machines-Screws A screw is an

inclined plane wrapped around a shaft or cylinder.

The inclined plane allows the screw to move itself when rotated.

Simple Machines-Lever The Lever

a rigid bar that is free to turn about a fixed point called the fulcrum

Every Lever has three (3) parts:

1.  Resistance Force, Input Force or Load, What you are trying to move or lift.

2.  Effort Force or Output Force - The work done on the Lever.

3.  Fulcrum – A fixed pivot point.

The Lever

1st Class Lever When the fulcrum is closer to the effort

than to the load: there is a loss in force

1st Class Lever When the fulcrum is closer to the load

than to the effort: There is a gain in force.

1st Class Lever When the fulcrum is midway between the

effort and the load: there is no change in force

1st Class Lever Examples:

Seesaw Crowbar Scissors

Increasing the Length of a Lever

If the size of scissors is increased than the amount of force exerted on their tip would be decreased.

Why use Levers? Using a lever is important because it

reduces the amount of force needed to lift an object.

2nd Class Levers

2nd Class Lever The load is between the effort and the

fulcrum. The fulcrum is at one end of the lever. The fulcrum is usually closer to the load. Produce a gain in force.

2nd Class Levers Examples:

Wheelbarrow Bottle opener Nutcrackers

3rd Class Levers The effort is between the load and the

fulcrum. There is usually a loss in force, but a gain

in speed and distance.

3rd Class Levers Examples:

Broom Shovel Fishing rod

Simple Machines Put Together Simple Machines can

be put together in different ways to make complex machinery.

This machinery where you use simple machines is now known as a compound or complex machine.

Rube Goldberg Website

Mechanical Advantage of a Lever

Mechanical Advantage is equal to the Effort Arm Distance divided by the Resistance Arm Distance.

If you place the effort arm two meters away from the fulcrum and the resistance two meters away from the fulcrum, what is the mechanical advantage?

Distance is measured in cm or meters

Maximizing Mechanical Advantage

Increasing the distance of the effort arm while decreasing the distance of the resistance arm allows you to gain more "power."

There is, however, the challenge that you cannot make the effort arm too long or it is too hard to use!

Which Smiley Face would be easier to move?

Lever Website

Mechanical Advantage of a Lever

The Mechanical Advantage of a Lever can also be calculated by using the forces.

MA=Resistance Force divided by the Effort Force

You apply a force of 18 N on to the end of a lever to open a paint can lid. The resistance of the lid is 9 N. Calculate the MA.

Force is measured in Newton's. (N)

Mechanical Advantage Questions

How could you increase the mechanical advantage of this lever?

Move the Fulcrum closer to the weight by doing so you increase the effort arm’s length! By doing so you extend the effort arm.

Mechanical Advantage Questions

Four levers were built and the effort measured as they lifted the same object. The effort for each is listed below:Lever A 0.5 NLever B 1 NLever C 2 NLever D 4 N

Which lever has the greatest mechanical advantage?

A

Lever Comparison Two levers were built

and the effort measured as they lifted a 2 kg object by 10 cm. The effort for each is listed below:Lever A 2 kgLever B 4 kgWhich lever did the most work?

They did the same amount of work.

Lever Comparison Which drawing

shows a lever that would need the least effort force to lift the weight?

The second drawing because the fulcrum is closest to the load!

How to keep shop windows clean.

Passing man (A) slips on banana peel (B) causing him to fall on rake (C). As handle of rake rises it throws horseshoe (D) onto rope (E) which sags, thereby tilting sprinkling can (F). Water (G) saturates mop (H). Pickle terrier (I) thinks it is raining, gets up to run into house and upsets sign (J) throwing it against non-tipping cigar ash receiver (K) which causes it to swing back and forth and swish the mop against window pane, wiping it clean. If man breaks his neck by fall move away before cop arrives.

Simplified Pencil Sharpener

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 in case opossum or the woodpecker gets sick and can't work.

Keep you From Forgetting to Mail a Letter For your Wife

As you walk past cobbler shop, hook (A) strikes suspended boot (B), causing it to kick football (C) through goal posts (D). Football drops into basket (E) and string (F) tilts sprinkling can, (G) causing water to soak coat tails (H). As coat shrinks, cord (I) opens door (J) of cage, allowing bird (K) to walk out on perch (L) and grab worm (M) which is attached to string (N). This pulls down window shade (O) on which is written, "YOU SAP, MAIL THAT LETTER." A simple way to avoid all this trouble is to marry a wife who can't write.

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Mythbusters Rube Goldberg

Honda’s Commercial with Rube Goldberg Invention