# CHAPTER 06 - WORK AND ENERGY | 9TH PHYSICS NOTES

Qasim Tariq 11-01-2020Notes

After studying this unit, the students will be able to:

• define work and its SI unit.
• calculate work done using equation
Work = force x distance moved in the direction of force
• define energy, kinetic energy and potential energy.
• State unit of energy.
• prove that kinetic energy K.E. = mv^2 and potential energy P.E. = mgh.
• Solve problems using these equations.
• list the different forms of energy with examples.
• describe the processes by which energy is converted from one form to another with reference to
fossil fuel energy
hydroelectric generation
solar energy
nuclear energy
geothermal energy
wind energy
biomass energy
• state mass energy equation E = mc^2 and solve problems using it.
• describe the process of electricity generation by drawing a block diagram of the process from fossil fuel input to electricity output.
• list the environmental issues associated with power generation.
• explain by drawing energy flow diagrams through steady state systems such as filament lamp, a power station, a vehicle travelling at a constant speed on a level road.
• differentiate energy sources as non renewable and renewable energy sources with examples of each.
• define efficiency of a working system and calculate the efficiency of an energy conversion using the formula: efficiency = energy output converted into the required form / total energy input
• explain why a system cannot have an efficiency of 100%.
• define power and calculate power from the formula: Power = work done / time taken
• define the unit of power "watt" in SI and its conversion with horse power.
• Solve problems using mathematical relations learnt in this unit.

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