Potential & Kinetic Energy

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Alabama Course of Study

• 10.) Differentiate between potential and kinetic energy.

• Examples:• - potential-rock resting at the top of a hill,• - kinetic-rock rolling down a hill• 11.) Explain the law of conservation of

energy and its relationship to energy transformation, including chemical to electrical, chemical to heat, electrical to light, electrical to mechanical, and electrical to sound.

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Energy

• Energy- ability to do work• 2 Types of Energy

– Kinetic– Potential

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Kinetic Energy• Kinetic Energy- energy of an object of

an object that is due to the object’s motion

• The object has kinetic energy if it is moving

– Kinetic energy=

– Kinetic energy increases as the mass or velocity increases

mv²

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Kinetic Energy

• What is the kinetic energy of a car has a mass if 1,200 kg and is moving at a speed of 20 m/s?

• KE=

• KE=

• KE=(480,000 kgXm/s²) /2• KE=240,000 kgXm/s²• Now do problems 1-4 on page 241

1,200 kg X (20m/s)²

21,200 kg X 400m/s²

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Kinetic Energy

• A bowling ball has a mass of 20kg and it is traveling at 2 m/s. What is it’s kinetic energy?

• A car with a mass of 200kg travels with a velocity of 10 m/s. What is it’s kinetic energy?

• A skier with a mass of 15kg travels with a velocity of 9.9m/s. What is it’s change in velocity?

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Potential Energy

• Potential Energy- energy that an object has because of the position, shape, or condition of the object

• The thing on earth that affects potential energy the most is gravity

• Height and weight after GPE the most– Gravitational potential energy=Weight X

Height

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Calculating GPE

• What is the GPE of a book with a weight of 13N at a height of 1.5m off the ground?

• GPE= Weight X Height• GPE=13N X 1.5m• GPE= 19.5 NXm or 19.5 J• Now do problems 1-3 on page 242

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GPE and Weight• A 500N skier is 40m off the ground. What

is his GPE?• A 600N skier is 40m off the ground. What

is his GPE?• The skier with a higher ______ has the

greater GPE.

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GPE and Height

• A 500N skier is 40m off the ground. What is her GPE?

• A 500N skier is 60m off the ground. What is her GPE?

• The skier with a higher _______ has the greater GPE.

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Elastic Potential Energy

•Elastic Potential Energy- energy associated with objects that can be stretched or compressed–Ex. When an archer pulls back a bow

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Roller Coasters and EnergyWhat energy is at

the top of the roller coaster?

What energy is at the bottom of the roller coaster?

What energy is here?

Or here?

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Potential, Kinetic, or Both?

• Rock rolling down a hill• Rock on the top of a hill• You sitting in a chair• You standing up• A penny sinking in a cup of water• Styrofoam ball floating in a cup of

water• Throwing a ball in the air

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Mechanical Energy

• Mechanical energy-form of energy associated with position and motion of an object

• ME=PE + KE• Ex. A football has 32 J of potential

energy and 45 J of kinetic energy. What is the ME?

• 32J + 45J= 77J

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You Teach Activity• Green-thermal energy pg449• Yellow- electrical energy pg 450• Blue- chemical energy pg 450• Pink- nuclear energy pg 450• Orange- electromagnetic energy pg

450 • Purple-Light energy (I will provide)• Red- sound energy (I will provide)• White- solar energy (I will provide)

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•4-5 Posters–No white–Must be named–Definition–1 fact–List 3 examples

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Law of Conservation of Energy

• Law of Conservation of Energy- energy cannot be created nor destroyed but can change from one form to another

• When energy is changed from one form to another, it is called an energy transfornmation

• Most forms of energy can be transformed into other forms

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Types of Transformations

• Single Transformation- one form of energy is changed into another one• Ex. Cell phone transforms electrical to

electromagnetic energy

• Multiple Transformations- more than change of form of energy– Match-chemical energy/to

thermal(heat)/ electromagnetic(light)18

Transformations between KE and PE

• One of the most common energy transformation is between potential energy and kinetic energy

• Look at pendulum on page 456– Copy picture and words

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Energy Transformations

Chemical to Heat

Chemical to Electrical

Electrical to Light

Light to Heat

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More Energy Transformations

Chemical to Electrical

Electrical to Mechanical

Mechanical to Sound

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