Work and simple_machines

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PhysicsPhysics

G9 MYP SciencesG9 MYP Sciences20132013

Mr. ErdosyMr. Erdosy 11

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G9 Physics Unit TopicsG9 Physics Unit Topics

Newton’s LawsNewton’s Laws

MomentumMomentum

ElectrostaticsElectrostatics

Simple MachinesSimple Machines

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Rube Goldberg ProjectRube Goldberg Project Create a Goldberg-style Contraption with at Create a Goldberg-style Contraption with at

least 3 stages to accomplish a simple task.least 3 stages to accomplish a simple task.

1 – Newton’s Laws1 – Newton’s Laws 2 – Momentum2 – Momentum 3 – Electrostatics3 – Electrostatics

Each must employ a Simple Machine.Each must employ a Simple Machine.

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Work and Simple Work and Simple MachinesMachines

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ENERGYENERGY

The textbook definition of The textbook definition of EnergyEnergy is: is:

THE ABILITY TO DO WORK.THE ABILITY TO DO WORK.

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WORKWORK

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Work is the transfer of Energy by applying a Force over a Distance

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Formula for workFormula for workWork = Force x DistanceWork = Force x Distance

The unit of force is The unit of force is NewtonsNewtons The unit of distance is metersThe unit of distance is meters The unit of work is The unit of work is Newton-metersNewton-meters One Newton-meter is equal to one JouleOne Newton-meter is equal to one Joule So, the unit of work is a So, the unit of work is a JouleJoule

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W=FdW=FdWork = Force x Work = Force x

DistanceDistance

Calculate: If a man Calculate: If a man pushes a concrete block pushes a concrete block 10 meters with a force 10 meters with a force of 20 N, how much of 20 N, how much work has he done?work has he done?

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W=FdW=FdWork = Force x Work = Force x

DistanceDistance

Calculate: If a man Calculate: If a man pushes a concrete block pushes a concrete block 10 meters with a force 10 meters with a force of 20 N, how much of 20 N, how much work has he done? work has he done? 200 200 joulesjoules

(W = 20N x 10m)(W = 20N x 10m)

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Fun Fact of the Fun Fact of the DayDay

The amount of The amount of caloriescalories you eat directly you eat directly determines the amount of work you are determines the amount of work you are able to do.able to do.

1 calorie = 4.18 Joules1 calorie = 4.18 Joules

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History of WorkHistory of Work

Before engines and motors were invented, people had to do Before engines and motors were invented, people had to do things like lifting or pushing heavy loads by hand. Using an things like lifting or pushing heavy loads by hand. Using an animal could help, but what they really needed were some animal could help, but what they really needed were some clever ways to either make work easier or faster. clever ways to either make work easier or faster.

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Simple MachinesSimple MachinesAncient people invented simple machines Ancient people invented simple machines

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

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Simple MachinesSimple Machines A simple machine makes Work easier by A simple machine makes Work easier by

providing a providing a Mechanical AdvantageMechanical Advantage. .

Changing the direction of a force.Changing the direction of a force. Increasing the Increasing the magnitudemagnitude of a force while of a force while

decreasing the distance it is applied.decreasing the distance it is applied. Decreasing the Decreasing the input forceinput force by increasing the by increasing the

distance it is applied.distance it is applied.

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Simple MachinesSimple Machines The six simple machines are:The six simple machines are:

Lever Lever Wheel and Axle Wheel and Axle Pulley Pulley Inclined Plane Inclined Plane Wedge Wedge Screw Screw

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The 3 Classes of The 3 Classes of LeversLevers

The class of a lever is The class of a lever is determined by the determined by the location of the location of the effort effort forceforce and the load and the load relative to the relative to the fulcrumfulcrum. .

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3 Classes3 Classes

To find the MA of a lever, divide the output force by the input force, or divide the length of the resistance arm by the length of the effort arm.

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First Class LeverFirst Class Lever In a first-class lever the fulcrum is located at In a first-class lever the fulcrum is located at

some point between the effort and resistance some point between the effort and resistance forces.forces. Common examples of first-class levers include Common examples of first-class levers include

crowbars, scissors, pliers, tin snips and seesaws. crowbars, scissors, pliers, tin snips and seesaws. A first-class lever always changes the direction of A first-class lever always changes the direction of

force (I.e. a downward effort force on the lever force (I.e. a downward effort force on the lever results in an upward movement of the resistance results in an upward movement of the resistance force). force).

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

Multiplies EF and changes its direction Multiplies EF and changes its direction

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Second Class Second Class LeverLever With a second-class lever, the load is located With a second-class lever, the load is located

between the fulcrum and the effort force.between the fulcrum and the effort force. Common examples of second-class levers include nut Common examples of second-class levers include nut

crackers, wheel barrows, doors, and bottle openers.crackers, wheel barrows, doors, and bottle openers. A second-class lever does not change the direction of A second-class lever does not change the direction of

force. When the fulcrum is located closer to the load force. When the fulcrum is located closer to the load than to the effort force, an increase in force than to the effort force, an increase in force (mechanical advantage) results. (mechanical advantage) results.

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RF (load) is between fulcrum and EF RF (load) is between fulcrum and EF Effort moves farther than Resistance.Effort moves farther than Resistance. Multiplies EF, but does not change its direction Multiplies EF, but does not change its direction

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Third Class LeverThird Class Lever With a third-class lever, the effort force is With a third-class lever, the effort force is

applied between the fulcrum and the applied between the fulcrum and the resistance force.resistance force. Examples of third-class levers include Examples of third-class levers include

tweezers, hammers, and shovels.tweezers, hammers, and shovels. A third-class lever does not change the A third-class lever does not change the

direction of force; third-class levers always direction of force; third-class levers always produce a gain in speed and distance and a produce a gain in speed and distance and a corresponding decrease in force. corresponding decrease in force.

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3rd Class 3rd Class LeverLever

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has the effort in the middle

effort arm is between the effort and the fulcrum

resistance arm is between the effort and the resistance

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EF is between fulcrum and RF (load) EF is between fulcrum and RF (load) Does not multiply force Does not multiply force

Resistance moves farther than Resistance moves farther than Effort.Effort.

Multiplies the distance the effort force Multiplies the distance the effort force travels travels

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AtlatlAtlatl

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Wheel and AxleWheel and Axle The wheel and axle is a The wheel and axle is a

simple machine simple machine consisting of a large consisting of a large wheel rigidly secured to wheel rigidly secured to a smaller wheel or shaft, a smaller wheel or shaft, called an axle. called an axle.

When either the wheel When either the wheel or axle turns, the other or axle turns, the other part also turns. One full part also turns. One full revolution of either part revolution of either part causes one full causes one full revolution of the other revolution of the other part. part.

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Fixed PulleyFixed Pulley A pulley can be used to A pulley can be used to

simply change the simply change the direction of a force or to direction of a force or to gain a mechanical gain a mechanical advantage, depending advantage, depending on how the pulley is on how the pulley is arranged. arranged.

A pulley is said to be a A pulley is said to be a fixed pulleyfixed pulley if it does not if it does not rise or fall with the load rise or fall with the load being moved. A fixed being moved. A fixed pulley changes the pulley changes the direction of a force; direction of a force; however, it does not however, it does not create a mechanical create a mechanical advantage. advantage.

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Moveable PulleyMoveable Pulley A A moveable pulleymoveable pulley rises and rises and

falls with the load that is falls with the load that is being moved. A single being moved. A single moveable pulley creates a moveable pulley creates a mechanical advantage; mechanical advantage; however, it does not change however, it does not change the direction of a force. the direction of a force.

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

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InclinedInclinedPlanePlane

An inclined plane is an An inclined plane is an even sloping surface. even sloping surface. The inclined plane The inclined plane makes it easier to makes it easier to move a weight from a move a weight from a lower to higher lower to higher elevation.elevation.

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Inclined Inclined PlanePlane

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

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

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WedgeWedge The wedge is a modification The wedge is a modification of the inclined plane. of the inclined plane. Wedges are used as either Wedges are used as either separating or holding separating or holding devices. devices.

A wedge can either be A wedge can either be composed of one or two composed of one or two inclined planes. A double inclined planes. A double wedge can be thought of as wedge can be thought of as two inclined planes joined two inclined planes joined together with their sloping together with their sloping surfaces outward. surfaces outward.

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ScrewScrew The screw is also a The screw is also a

modified version of modified version of the inclined plane. the inclined plane.

While this may be While this may be somewhat difficult somewhat difficult to visualize, it may to visualize, it may help to think of the help to think of the threads of the threads of the screw as a type of screw as a type of circular ramp (or circular ramp (or inclined plane). inclined plane).