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WHAT IS ENERGY NEEDED FOR? |
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Definition
To make stationary objects move
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Term
PRINCIPLE OF CONSERVATION OF ENERGY |
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| Energy can't be created or destroyed |
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| Work is done on an object when a force acting on it makes it move |
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| = Force x distance moved in direction of force |
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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 |
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Definition
| Area under graph = work done because W=Fs |
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WORK DONE TO STRETCH SPRING TO EXTENSION |
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Definition
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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 |
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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
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Definition
| Only if distance is smaller than earths radius because force of gravity decreases above earth |
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ENERGY CHANGES INVOLVING KINETIC AND POTENTIAL ENERGY |
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Definition
Object gains speed as it falls if air resistance is negligible. This decreases potential energy and increase kinetic energy
1/2mv2 = mgh |
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Kinetic energy = loss of potential energy from maximum height
1/2 mv2 = mg(h0 - h) |
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WORK DONE TO OVERCOME FRICTION AND AIR RESISTANCE |
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Definition
w = mgh -1/2mv2
h = vertical distance between top and bottom |
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Term
HOW CAN ENERGY BE TRANSFERRED? |
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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 |
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Definition
| The more energy transferred per second, the greater the power of the transfer |
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The rate of transfer of energy
P = E / t
P = W / t |
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=Weight x height gain / time
= energy transferred / time |
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Definition
| Measured using joulemeter |
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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 |
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Term
WHEN A POWERED OBJECT GAINS SPEED |
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Definition
Output force exceeds resistive forces on it
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Definition
| = energy wasted per second (resistive) + gain of kinetic energy per second |
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Definition
Apply a force on the object to move it through a distance
work = Fs
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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 |
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Definition
Useful energy transfer.
Efficiency of a machine = useful energy / total energy
= work done / total energy
= output power / input power
% efficiency = efficiency x 100 |
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Term
RENEWABLE ENERGY OVERVIEW |
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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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