P8
- Created by: ak27330
- Created on: 05-01-20 16:13
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- P8
- Energy Transfers and Systems
- system change, energy transferred. Closed system- net change in energy is 0
- some energy dissipates, efficiency is the proportion of the total energy supplied that ends up in useful stores
- Energy is transferred mechanically when work is done by or against a force
- Heating transfer from thermal of hot object to thermal of cold
- Work Done
- Work done is the energy transferred when a force acts on an object
- When something moves, effort is needed
- E = F x d
- E = work done(J) F= Force(N) d= distance(m)
- ?GPE = mg x ?h
- KE = 0.5 x mv²
- Dissipation of Energy
- Some energy dissipates to thermal energy of a moving object
- Push something along a rough surface, work against frictional forces
- Transferred to kinetic store, some to thermal due to friction. Increases temp
- Lubricants can be used to reduce friction between objects
- efficiency= useful energy/ total energy
- Power
- rate of energy transfer, or the rate of doing work
- P=E/t
- P - power(w) E - work done(J) t -time(s)
- Powerful machine, transfers lots of energy quickly
- Energy Transfers and Systems
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