oneSK-17B

Objective: To apply formulas for energy in order to determine the amount of energy of an object Core Question: Can objects have both potential and kinetic energy at the same time?Drill: 1. Review your homework paper. 2. Do you have any energy questions?

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Come up with an original example of kinetic energy and an original example of potential energy. Be prepared to support your ideas. 

Kinetic:Potential:

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Pendulum AnalysisWhen does a pendulum have the most kinetic energy?

At the bottom of its swingWhen does a pendulum have the most potential energy?

At the top of its swing

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Video: http://www.youtube.com/watch?v=Jnj8mc04r9E

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Formula Practice: Summary Notes

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Ex. 1 - An object is traveling at a constant velocity of 8 m/s. It has a mass of 42 kg. What is its

kinetic energy? 

kinetic energy = mass x velocity2

2kinetic energy = 42 kg x (8 m/s) 2

2kinetic energy = 42 kg x 64 m2/s2

2 kinetic energy = 2688 kg m2/s2

2 kinetic energy = 1344 J

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oneSK-17B

Ex. 2 – What is the weight in newtons of a 45 kg child? weight (newtons) = mass × gravitational accelerationweight (newtons) = 45 kg × 9.8 m/s2

weight (newtons) = 441 N

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Ex. 3 - An 8 N object is suspended at a height of 25 m. What is its

potential energy? gravitational potential energy = weight x height  gravitational potential energy = 8 N x 25 m  gravitational potential energy = 200 N-m

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Ex. 4 - A 4 kg object is suspended at a height of 5m. What is its potential energy? grav.potential energy = mass x grav. acceleration x height grav.potential energy = 4 kg x 9.8 m/s2 x 5 m grav. potential energy = 39.2 kg m/s2 x 5 m grav.potential energy = 196 J

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oneSK-17B

Try This: A 25 kg object is falling through the air. At a height of 10 m it has a velocity of 85 m/s. Calculate both the kinetic and potential energy of the object. What is the object’s total energy?

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oneSK-17B

KINETIC ENERGY 

kinetic energy = mass x velocity2

2 kinetic energy = 25 kg x (85 m/s) 2

2 kinetic energy = 25 kg x 7225 m2/s2

2 kinetic energy = 180,625 kg m2/s2

2 kinetic energy = 90,312.5 J

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Potential Energy grav.potential energy = mass x grav. acceleration x height grav.potential energy = 25 kg x 9.8 m/s2 x 10 m grav. potential energy = 245 kg m/s2 x 10 m grav.potential energy = 2450 J

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TOTAL ENERGY

TE = Kinetic Energy + Potential Energy

TE = 90,312.5 J + 2450 J

TE = 92,762.5 J

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Homework:

Energy Problems – Show all work using proper form.

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