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Work and Simple Work and Simple MachinesMachines

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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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Simple MachinesSimple Machines

A machine is a device that helps A machine is a device that helps make work easier bymake work easier by transferring a force from one place to transferring a force from one place to

anotheranother changing the direction of a force changing the direction of a force

increasing the size of a forceincreasing the size of a force increasing the distance or speed of a increasing the distance or speed of a

force. force.

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Mechanical AdvantageMechanical Advantage input forceinput force (the force you apply) (the force you apply)

and the and the outputoutput forceforce (force which is (force which is applied to the task).applied to the task).

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

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The LeverThe Lever

A lever is a rigid bar that rotates A lever is a rigid bar that rotates around a fixed point called the around a fixed point called the fulcrum.fulcrum.

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The 3 Classes of LeversThe 3 Classes of Levers

determined by:determined by:

location of the effortlocation of the effort

force and the loadforce and the load

compared to thecompared to the

fulcrum. fulcrum.

The workman uses a trolley to move the large packing case. The fulcrum is the wheel.

First Class LeverFirst Class Lever

In a first-class lever the fulcrum is located In a first-class lever the fulcrum is located at some point between the effort and at some point between the effort and resistance forces.resistance forces.

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

Second Class LeverSecond Class Lever

The gardener uses a wheel barrow to lift tools and garden waste. The load is in the centre of the barrow

With a second-class lever, the load is With a second-class lever, the load is located between the fulcrum and the located between the fulcrum and the effort force.effort force.Common examples of second-class Common examples of second-class levers include nut crackers, wheel levers include nut crackers, wheel barrows, doors, and bottle openers.barrows, doors, and bottle openers.

Third Class LeverThird Class Lever

The fisherman catches the fish which becomes the load at the end of the lever.

With a third-class lever, the With a third-class lever, the effort force is applied between effort force is applied between the fulcrum and the resistance the fulcrum and the resistance force.force.

Examples of third-class Examples of third-class levers include tweezers, levers include tweezers, hammers, and shovels.hammers, and shovels.

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Wheel and AxleWheel and Axle

consist of a large consist of a large wheel connected to wheel connected to a shaft called an a shaft called an axle. axle.

When either the When either the wheel or axle wheel or axle turns, the other turns, the other part also turns. part also turns.

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PulleyPulley

A pulley consists of a grooved A pulley consists of a grooved wheel that turns freely in a wheel that turns freely in a frame called a block.frame called a block.

A A fixed pulleyfixed pulley does not rise or does not rise or fall with the load being fall with the load being moved. moved.

A A moveable pulleymoveable pulley rises and rises and falls with the load that is falls with the load that is being moved. being moved.

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Inclined PlaneInclined Plane

An inclined plane is An inclined plane is ramp The inclined ramp The inclined plane makes it plane makes it easier to move a easier to move a weight from a weight from a lower to higher lower to higher elevation.elevation.

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WedgeWedge The wedge is a The wedge is a

modification of the modification of the inclined plane. inclined plane. Wedges are used as Wedges are used as either separating or either separating or holding devices. holding devices.

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ScrewScrew

Think of the 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).

1515

What’s work?What’s work? A scientist delivers a speech to an A scientist delivers a speech to an

audience of his peers. audience of his peers. A body builder lifts 350 pounds A body builder lifts 350 pounds

above his head. above his head. A mother carries her baby from room A mother carries her baby from room

to room. to room. A father pushes a baby in a carriage.A father pushes a baby in a carriage. A woman carries a 20 kg grocery bag A woman carries a 20 kg grocery bag

to her car? to her car?

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What is work?What is work?

In science, the word In science, the word workwork has a has a different meaning than you may be different meaning than you may be familiar with.familiar with.

The scientific definition of work is: The scientific definition of work is: using a force to move an object a using a force to move an object a distancedistance

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Work or Not?Work or Not?

According to the According to the scientific definition, scientific definition, what is work and what is work and what is not?what is not? a teacher lecturing a teacher lecturing

to a classto a class a mouse pushing a a mouse pushing a

piece of cheese piece of cheese with its nose across with its nose across the floorthe floor

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What’s work?What’s work? A scientist delivers a speech to an A scientist delivers a speech to an

audience of his peers. audience of his peers. A body builder lifts 350 pounds A body builder lifts 350 pounds

above his head. above his head. A mother carries her baby from room A mother carries her baby from room

to room. to room. A father pushes a baby in a carriage.A father pushes a baby in a carriage. A woman carries a 20 kg grocery bag A woman carries a 20 kg grocery bag

to her car? to her car?

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What’s work?What’s work? A scientist delivers a speech to an A scientist delivers a speech to an

audience of his peers. audience of his peers. NoNo A body builder lifts 350 pounds A body builder lifts 350 pounds

above his head. above his head. YesYes A mother carries her baby from room A mother carries her baby from room

to room. to room. NoNo A father pushes a baby in a carriage. A father pushes a baby in a carriage. YesYes A woman carries a 20 km grocery A woman carries a 20 km grocery

bag to her car? bag to her car? NoNo

2020

Formula for workFormula for work

Work = Force x DistanceWork = Force x Distance

The unit of work is a The unit of work is a joulejoule

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W=FDW=FD

Work = Force x Work = Force x DistanceDistance

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

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W=FDW=FD

Work = Force x Work = Force x DistanceDistance

Calculate: If a Calculate: If a man pushes a man pushes a concrete block 10 concrete block 10 meters with a meters with a force of 20 N, how force of 20 N, how much work has he much work has he done? done? 200 joules200 joules(W = 20N x 10m)(W = 20N x 10m)

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PowerPower Power is the rate at which work is Power is the rate at which work is

done. done.

Power = WorkPower = Work**/Time/Time **(force x distance)(force x distance)

The unit of power is the watt.The unit of power is the watt.