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1.1 Energy in Physics Monday, January 18, 2021 Analogy with Money 13:42 Energy and money; familiar with 1t, know how to use it, transfer 1t.. Gabriel's Wealth: Transfer is within Gabriel's Wealth Inflow is from outside TO Gabriel's Wealth Outflow is from Gabriel's Wealth TO outside Initial | Transfe | Transfe | Inflow | Outflow r r Wallet| 408 1208 208 208 108 Investments| 1.,000$ | 1,0008| 1,1008 | 1,100S| 1,100 $ Checking | 4608 | 3808 | 3808 | 880% | 880% Account Wealth 1,5008 1,500S 15008 2,000 19908 The same can be said about Energy. We can define a certain system; » The energy transferred within that system doesn’t change the total energy. » If an outside source send energy to the system, Total Energy increase. » If an outside source takes energy from the system, Total Energy decrease. Work and Energy in Physics < The words "Energy”" and "Work" mean different things in different contexts. < In physics we are more specific about all our definitions. Energy: Ability to do Work Work: Transfer of Energy This 1s somewhat of a circular definition. However 1t 1s sufficient to explain many physical systems and make calculations and predictions about the natural world. It 1s one of the most important concepts in physics. Work <+ The word work means many things in everyday life. < We defined work as: the transfer of energy <> For example, this guy pushes a box across the floor he 1s transferring energy into the box. ~ work == force ' distance <> The work done on the box 1s defined as the product of the force times the distance he pushes the box Examples of Work You liftalkg box up 2 meters @ You hold a 1 kg box without moving 1t for an hour Both exerted the same force on the box, but only the first person did Work. To have work you need a force applied AND the box needs to move (distance). Work = Force x Distance