WORK AND SIMPLE MACHINES: Let’s try a quick “pre-assessment”

WORK AND SIMPLE MACHINES:

Let’s try a quick “pre-assessment”

Energy:Ability to do work (calories)

Force applied x Distance (Newton-meter)

Force: A Push or a Pull (N)

Definition overview:

Work over a period of time (watt)

Power:

Work is force done over a distance.

The formula is: W = F x d

-force is expressed in Newtons (N)

-distance is expressed in meters (m)

-Work is done in N-m… or Joules (J)

The work triangle looks like this:

Simple MachinesAncient people invented simple

machines that would help them overcome resistive forces and allow them to do the desired work against those forces.

Simple Machines The six simple machines are:

Lever: 1st, 2nd, 3rd Wheel and Axle Pulley Inclined Plane Wedge Screw

Write these down on your notesheet in the 8 boxes. There are 3 boxes for levers.

Simple MachinesA machine is a device that helps

make work easier to perform by accomplishing one or more of the following functions: changing the direction of a force, increasing the magnitude of a force,

or increasing the distance or speed of a

force.

Mechanical Advantage It is useful to think about a

machine in terms of the input force (the force you apply) and the output force (force which is applied to the task).

When a machine takes a small input force and increases the magnitude of the output force, a mechanical advantage has been produced.

Mechanical Advantage Mechanical advantage is the ratio of output

force divided by input force. If the output force is bigger than the input force, a machine has a mechanical advantage greater than one.

If a machine increases an input force of 10 pounds to an output force of 100 pounds, the machine has a mechanical advantage (MA) of 10.

In machines that increase distance instead of force, the MA is the ratio of the output distance and input distance.

MA = output/input

No machine can increase both the magnitude and the distance of a force at the same time.

The 6 Simple MachinesLever x 3

classes

Pulley Wheel and Axle

WedgeScrew

Inclined Plane

Fulcrum is between EF (effort) and RF (load)Effort moves farther than Resistance. Multiplies EF and changes its direction

The mechanical advantage of a lever is the ratio of the length of the lever on the applied force side of the fulcrum to the length of the lever on the resistance force side of the fulcrum.

First Class Lever

First Class Lever.

Common examples of first-class levers include crowbars, scissors, pliers, tin snips and seesaws.

RF (load) is between fulcrum and EF Effort moves farther than Resistance.

Multiplies EF, but does not change its direction The mechanical advantage of a lever is the ratio of the distance from the applied force to the fulcrum to the distance from the resistance force to the fulcrum.

Second Class Lever

Second Class LeverExamples of

second-class levers include nut crackers, wheel barrows, doors, and bottle openers.

EF is between fulcrum and RF (load) Does not multiply force Resistance moves farther than Effort. Multiplies the distance the effort force travels

The mechanical advantage of a lever is the ratio of the distance from the applied force to the fulcrum to the distance of the resistance force to the fulcrum

Third Class Lever

Third Class LeverExamples of

third-class levers can include tweezers, arm hammers, and shovels.

The bicep = 1st class

Inclined Plane

Inclined Plane The Egyptians used simple machines to build the

pyramids. One method was to build a very long incline out of dirt that rose upward to the top of the pyramid very gently. The blocks of stone were placed on large logs (another type of simple machine - the wheel and axle) and pushed slowly up the long, gentle inclined plane to the top of the pyramid.

Inclined Planes An inclined plane is

a flat surface that is higher on one end

Inclined planes make the work of moving things easier

Work input and outputWork input is the amount of work

done on a machine. Input force x input distance

Work output is the amount of work done by a machine.Output force x output distance

Wout = Win

Fout x Dout = Fin x Din

10N x 3m = 2N x 15m 10 NFin(E)

Din(E)Dout(R)

Inclined Plane -Mechanical Advantage

The mechanical advantage of an inclined plane is equal to the length of the slope divided by the height of the inclined plane.

While the inclined plane produces a mechanical advantage, it does so by increasing the distance through which the force must move.

The mechanical advantage of an screw can be calculated by dividing the circumference by the pitch of the screw.

Pitch equals 1/ number of turns per inch.

Pulleys Pulley are wheels

and axles with a groove around the outside

A pulley needs a rope, chain or belt around the groove to make it do work

Diagrams of Pulleys

Fixed pulley: A fixed pulley changes the direction of a force; however, it does not create a mechanical advantage.

Movable Pulley: The mechanical advantage of a moveable pulley is equal to the number of ropes that support the moveable pulley.

COMBINED PULLEY The effort needed to

lift the load is less than half the weight of the load.

The main disadvantage is it travels a very long distance.

Wedges Two inclined

planes joined back to back.

Wedges are used to split things.

Wedge – Mechanical Advantage The mechanical advantage of a wedge can be found

by dividing the length of either slope (S) by the thickness (T) of the big end.

As an example, assume that the length of the slope is 10 inches and the thickness is 4 inches. The mechanical advantage is equal to 10/4 or 2 1/2. As with the inclined plane, the mechanical advantage gained by using a wedge requires a corresponding increase in distance.

WHEEL AND AXEL The axle is stuck

rigidly to a large wheel. Fan blades are attached to the wheel. When the axel turns, the fan blades spin.

Wheel and Axel The mechanical advantage of a wheel and axle is the

ratio of the radius of the wheel to the radius of the axle.

In the wheel and axle illustrated above, the radius of the

wheel is five times larger than the radius of the axle. Therefore, the mechanical advantage is 5:1 or 5.

The wheel and axle can also increase speed by applying the input force to the axle rather than a wheel. This increase is computed like mechanical advantage. This combination would increase the speed 5 times.

GEARS-Wheel and Axel Each gear in a

series reverses the direction of rotation of the previous gear. The smaller gear will always turn faster than the larger gear.

Formulas: IMA = DE

DRAMA = FR

FEOUTPUT = FR X DR INPUT = FE X DEEFFICIENCY = OUTPUT = AMA

INPUT IMA

Note:AMA – always less than IMAOUTPUT – always less than INPUT

The next slides contain calculations you must know: Lever:

All 3 classes

MA and Efficiency of AMA to IMA

FR x DR = FE x DE

Inclined Plane: Mechanical

advantage

Overall efficiency is based on IMA compared to AMA

What will the FE be? FR x DR = FE x DE

FR = 40N

FE = 10N

Wheel and Axle MA or IMA Efficiency of AMA to

What will the FE be? FR x DR = FE x DE

FR = 10N

DE = 15cm

DR = 3cm

FE = 2N

Wedge IMA:How long divided by how fat/wide.

Pulley IMA Count the strings involved as the support.

Pulling down - count and subtract 1 Pulling up – count them all

Screw:You do not have to calculate this one

other than on your rube.

Videos:

http://study.com/academy/lesson/simple-machines-lever-inclined-plane-pulley.html

Bill Nye ??

Ed-Heads:

You will complete all 5 of the given activities and send a screen shot word doc of each final score.

Rube Goldberg Machines Rube Goldberg machines are

examples of complex machines. All complex machines are made

up of combinations of simple machines.

Rube Goldberg machines are usually a complicated combination of simple machines.

By studying the components of Rube Goldberg machines, we learn more about simple machines

When you slip on ice, your foot kicks paddle (A), lowering finger (B), snapping turtle (C) extends neck to bite finger, opening ice tongs (D) and dropping pillow (E), thus allowing you to fall on something soft.

Safety Device for Walking on Icy Pavements

Honda Commercial

https://www.youtube.com/watch?v=YWk9N92-wvg

Marble Fun Video

https://www.youtube.com/watch?v=NzAQ-jYfEqA

Squeeze Orange JuiceRube Goldberg Machine

https://www.youtube.com/watch?v=uzZVamELN2E

Simple machine computer lesson/quest:

http://www.cosi.org/downloads/activities/simplemachines/sm1.html

You must complete each section of the exercise:-I need a screen shot of the “Find the Simple Machine”-I need a screen shot of the

“Putting Simple Machines to Work” test

WORK AND SIMPLE MACHINES: Let’s try a quick “pre-assessment”

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