# Shared Flashcard Set

## Details

Work, energy and power
N/A
29
Physics
Not Applicable
10/20/2012

Term
 WHAT IS ENERGY NEEDED FOR?
Definition
 To make stationary objects move
Term
 PRINCIPLE OF CONSERVATION OF ENERGY
Definition
 Energy can't be created or destroyed
Term
 WORK
Definition
 Work is done on an object when a force acting on it makes it move
Term
 WORK DONE
Definition
 = Force x distance moved in direction of force
Term
 FORCE AND DISPLACEMENT
Definition
 Components yacht with force at angle θ to the direction of movement Fsinθ is the upward force   work done = Fcosθ   if θ = 90º (force perpendicular to direction) then work done = 0
Term
 FORCE DISTANCE GRAPHS
Definition
 Area under graph = work done because W=Fs
Term
 WORK DONE TO STRETCH SPRING TO EXTENSION
Definition
 W = 1/2 FL
Term
 KINETIC ENERGY
Definition
 Energy of an object due to it's motion.    Faster it moves, higher kinetic energy   Ek = 1/2 mv2   Gain of kinetic energy is due to work done
Term
 POTENTIAL ENERGY
Definition
 Energy due to an object due to it's position Object of a certain mass raised through height at constant speed force needed to raise is equal and opposite to weight (mg)  work done = Fs = mgh Work done on object increases it's GPE   EP= mgh
Term
 WHERE DOES MGH APPLY?
Definition
 Only if distance is smaller than earths radius because force of gravity decreases above earth
Term
 ENERGY CHANGES INVOLVING KINETIC AND POTENTIAL ENERGY
Definition
 Object gains speed as it falls if air resistance is negligible. This decreases potential energy and increase kinetic energy   1/2mv2 = mgh
Term
 A PENDULUM BOB
Definition
 Kinetic energy  = loss of potential energy from maximum height   1/2 mv2 = mg(h0 - h)
Term
 WORK DONE TO OVERCOME FRICTION AND AIR RESISTANCE
Definition
 w = mgh -1/2mv2   h = vertical distance between top and bottom
Term
 HOW CAN ENERGY BE TRANSFERRED?
Definition
 Work done by a force due to one object making the other move    Heat transfer from hot to cold   Electromagnetic radiation, sound waves and electricity
Term
 POWER AND ENERGY
Definition
 The more energy transferred per second, the greater the power of the transfer
Term
 POWER
Definition
 The rate of transfer of energy     P = E / t   P = W / t
Term
 MUSCLE POWER
Definition
 =Weight x height gain / time   = energy transferred / time
Term
 ELECTRICAL POWER
Definition
 Measured using joulemeter
Term
 ENGINE POWER
Definition
 Output power of an engine = motive power   When a powered oject moves at constant velocity at constant height, resistive forces are equal and opposite to motive force   Work done by engine converted into internal energy of surroundings    P = Fv
Term
 WHEN A POWERED OBJECT GAINS SPEED
Definition
 Output force exceeds resistive forces on it
Term
 MOTIVE POWER
Definition
 = energy wasted per second (resistive) + gain of kinetic energy per second
Term
 MACHINES
Definition
 Apply a force on the object to move it through a distance work  = Fs
Term
 MACHINE OUTPUT
Definition
 Object moves at constant velocity due to force being opposed by equal and opposite forces caused by friction   POUT = Work done / time = Fvt / t = Fv
Term
 EFFICIENCY
Definition
 Useful energy transfer.    Efficiency of a machine = useful energy / total energy   = work done / total energy   = output power / input power   % efficiency = efficiency x 100
Term
 WIND POWER*
Definition
Term
 WATER POWER*
Definition
Term
 SOLAR POWER*
Definition
Term
 RENEWABLE ENERGY OVERVIEW
Definition
 Electricity uses 30% energy supply Solar panels - crap Wind farms - bit better Hydroelectric - ok Ground source can contribute slightly. Natural renewables are unreliable(e.g more resevoirs)  Better insulation in homes, more efficient machines, reduce carbon emissions Transport needs to switch from fossil fuels to reduce more CO2 emissions
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