physical science ch. 5. work the transfer of energy that occurs when a force makes an object...
TRANSCRIPT
Physical SciencePhysical Science
Ch. 5Ch. 5
WorkWork• The transfer of energy The transfer of energy
that occurs when a force that occurs when a force
makes an object move.makes an object move.
• Motion is in direction of Motion is in direction of
applied force.applied force.
WorkWork
Work = Force*distanceWork = Force*distance
Work is measured in JoulesWork is measured in Joules
Joule is a Newton-meterJoule is a Newton-meter
J = N * mJ = N * m
PowerPower
• The amount of work done The amount of work done
in a certain amount of in a certain amount of
time.time.
• The rate at which work is The rate at which work is
done.done.
PowerPower
Power =Power = workwork = = EnergyEnergy timetime timetime
Power = Power = Force*distanceForce*distance timetime
MachinesMachines• Make work easierMake work easier• Simple machineSimple machine
–Does work in only one Does work in only one directiondirection
• Complex machineComplex machine–Does work in more than one Does work in more than one
directiondirection–Combination of more than Combination of more than
one simple machineone simple machine
Simple MachinesSimple Machines
• Incline PlaneIncline Plane
• WedgeWedge
• ScrewScrew
• LeverLever
• PulleyPulley
• Wheel & AxleWheel & Axle
• Incline PlaneIncline Plane–Sloping surface that reduces the Sloping surface that reduces the
amount of force required to do workamount of force required to do work
• WedgeWedge–An incline plane with sloping sidesAn incline plane with sloping sides
–A moveable incline planeA moveable incline plane
• ScrewScrew–An incline plane wrapped in a spiral An incline plane wrapped in a spiral
around a cylindrical postaround a cylindrical post
• LeverLever–Bar that is free to pivot or turn Bar that is free to pivot or turn
about a fixed pointabout a fixed point
• PulleysPulleys–Grooved wheel with a rope Grooved wheel with a rope
running along the groove.running along the groove.
• Wheel & AxleWheel & Axle–2 wheels of different sizes that 2 wheels of different sizes that
rotate togetherrotate together
• A machine where work A machine where work
input equals to work outputinput equals to work output
–Will never exist because of Will never exist because of
frictionfriction
WWinputinput = W = Woutputoutput
Ideal MachinesIdeal Machines
• Mechanical AdvantageMechanical Advantage–Number of times a machine Number of times a machine
multiplies the effort forcemultiplies the effort force• EfficiencyEfficiency
–Measure of how much the Measure of how much the work input is changed into work input is changed into usefuluseful work output work output
Efficiently = Efficiently = WWoutout x 100% x 100% WWinin