Presentation on theme: "Chapter 13: Work and Energy"— Presentation transcript:
1 Chapter 13: Work and Energy Section 3: What is energy?
2 Energy and workWhenever work is done, energy is transformed or is transferred from one system to another systemDefinition of energy: The ability to do workEnergy comes in many forms:NuclearChemicalMechanicalHeatSoundEnergy is measured in Joules (J)… just like work!The ones we are talking about in physical science.
3 Types of Mechanical Energy POTENTIAL ENERGYKinetic energyThe energy that an object has because of the position, shape, or condition of the object.Two types:Elastic potential energyGravitational potential energyThe energy that an object has due to the object’s motion𝐾𝐸= 1 2 𝑚 𝑣 2𝑃𝐸 𝑔 =𝑚𝑔ℎTotal mechanical energy = PE + KE
4 More about Potential Energy Sometimes this type of energy is referred to as Stored energyElastic potential energy depends on how stretched or compressed the object isGravitational potential energy depends onThe mass of the objectThe relative heightRelative to where the reference point is defined
5 More about kinetic energy Kinetic energy depends onThe mass of the objectHow fast the object is movingBecause velocity is squared, KE depends on speed more than massAtoms and molecules have kinetic energy, because they are always moving.
6 Other forms of energy Chemical reactions involve potential energy Photosynthesis is the process that turns energy from the sun into chemical energy that is stored in sugars and other molecules in cellsWhen you eat, you are eating stored energy… potential energyThe sun gets energy from nuclear reactions, called nuclear fusionEnergy can be stored in fieldsEarth’s gravitational field stores gravitational potential energyElectric fields store electrical energy