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14 Cards in this Set
- Front
- Back
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Work |
Force multiplied by distance moved in the direction of the force |
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KE |
the energy possessed by an object by virtue of its motion |
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What if theta is > 90 between force and distance |
work is negative e.g friction opposes direction of motion, so negative work done on object |
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GPE |
The energy possessed by an object by vitue of its position in a gravitatonal field |
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EPE |
Energy possess by an object by virtue of its deformation |
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EPE formula |
1/2 fx 1/2k x ^2 1/2 F^2 / k |
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Power |
Rate of energy transfer. If energy transfer done by work then it is rate of doing work |
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Dissipatieve forces |
Forces which lead to a loss in mechanical energy in a system. E.g friction, fluid resistance |
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Internal energy |
Sum of random kinetic and potential energies of individual particles in system. (thermal energy) |
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energy transfer with friction |
work against friction/ dissipative force results in energy transfer to random motion of individual particles / internal energy |
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compare usefulness of internal energy vs KE/PE of whole system
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motion in KE is ordered. PE requires all particles in system to have been displaced in ordered way. However, no way of coaxing randomly vibrating moelcules to move in same direction -> therefore energy is less useful |
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internal energy for skydiver |
drag results in transfer of energy to eddy motions in air which dissipate into internal energy of air molecules. At terminal speed, the rate of loss of GPE is equal to rate of increase in atmospheric internal energy |
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'analyse' energy transfer meaning |
Means give an energy transfer equation with all value calculated |
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efficiency |
Fraction of input energy which is usefully transferred |
