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NIS – PHYSICAL SCIENCE

NIS – PHYSICAL SCIENCE. Lecture 15 The Nature of Energy Ozgur Unal. Energy. Energy is the ability to do work . Or , energy is the ability to cause a change . The ball in F igure 1 is moving and it has the ability to break the window glass. What is work ?. Examples :

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NIS – PHYSICAL SCIENCE

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  1. NIS – PHYSICAL SCIENCE Lecture 15 TheNature of Energy OzgurUnal

  2. Energy • Energyis theabilityto do work. • Or, energyis theabilitytocause a change. • Theball in Figure 1 is movingand it has theabilityto break thewindowglass. What is work? • Examples: • An apple on a tree has theabilitytocause a changeif it fallsdown, so it has energy. • Thesunlight has theabilitytocause a change (tanning), so it has energy. • Heat has theabilitytocause a change (cookingfood), so it has energy.

  3. DifferentForms of Energy • Energy can takedifferentforms: • Thermalenergy • Radiantenergy • Chemicalenergystored in foodsandfuels • Electricalenergyetc.

  4. KineticEnergy • Whichobjectwouldcause a greaterchange? • 1- A lightobjector a heavyobjectmoving at thesamespeeds? • 2- Twosameobjectsmoving as differentspeeds? Energyduetomotion is calledkineticenergy. Everymovingobject has kineticenergy. • Aheavyobject has morekineticenergythan a lightobjectmoving at thesamespeed. • Afasterobject has morekineticenergythan a slowerobjectwiththesamemass.

  5. KineticEnergy Kineticenergy: KE = m * v2 / 2 Theunit of energy is Joule (J). Express joule in terms of baseunits. Is energy a vector? • Example: What is thekineticenergy of a baseballmoving at a speed of 40 m/s ifthebaseball has a mass of 0.15 kg?

  6. PotentialEnergy Energydoesn’thavetoinvolvemotion. Storedenergyduetoposition is calledpotentialenergy. An objectwith a certainheight has thepotentialtocause a changeif it start fallingdown. • Examplesforpotentialenergy: • Elasticpotentialenergy is energy • storedbysomethingthat can • stretchorcompress. • Observethespringsgiventoyou • andexplainhowenergy can be • stored in it.

  7. PotentialEnergy Examplesforpotentialenergy: Foodsandfuelscontainstoredenergy in chemicalbonds. Energystored in chemicalbonds is calledchemicalpotentialenergy. CheckoutFigure 3! Energy is stored in thebondsthat holdthecarbonandhydrogen atomstogetherand is released whenthegas is burned.

  8. NIS – PHYSICAL SCIENCE Lecture 16 GravitationalPotentialEnergy OzgurUnal

  9. GravitationalPotentialEnergy • GPE = m * g * h • What is theunit of GPE? • Is GPE a vector? Anythingthat can fall has storedenergycalledgravitationalpotentialenergy (GPE). • Example: Findtheheight of a baseballwith a mass of *.15kg that has a GPE of 73.5 J.

  10. GravitationalPotentialEnergy Whichobjecthas thegreatestpotentialenergy?

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