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Energy

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Energy

- Energy is the ability to cause change
- Any time you move, or move something you are using energy

- What are some forms of energy?
- Electrical – energy in the form of moving electrons
- Chemical – energy from a chemical reaction
- Thermal – energy of heat
- Radiant – the energy of electromagnetic waves including light, gamma rays, microwaves

- Energy can be converted between it’s different forms
- Radiant Energy is converted to chemical energy through photosynthesis

- Chemical energy is turned into thermal energy in a fire.

- Thermal energy is turned into electrical in a power plant.

- Electrical energy is turned into radiant energy in a lightbulb.

- Kinetic energy is the energy of movement
- KE = ½ mv2
- m is the mass of an object, v is the velocity of an object
- Standard units – kg m2/s2 or Joules (J)

- A jogger who’s mass is 60 kg is moving at 3 m/s, what is the jogger’s kinetic energy?
- m = 60 kg, v = 3 m/s
- KE = 1/2(60kg)(3 m/s)2 = 270 J

- A car moving at a speed of 20 m/s has a KE of 300,000 J. What is the car’s mass?

- A sprinter has a mass of 62.5 kg and a KE of 4000 J. What is the sprinter’s velocity?

- Potential energy is stored energy
- 5 Types of Potential Energy
- Elastic
- Chemical
- Electrical
- Nuclear
- Gravitational

- Elastic Potential Energy is energy stored by something that can stretch or compress

- Chemical Potential Energy is the energy stored in the chemical bonds between atoms.

- Electrical Potential Energy is the energy due to the position of an electric charge

- Nuclear Potential Energy is the energy stored in the nucleus of an atom
- If you could release all of the nuclear potential energy in you body, you could power the United States for 6 years.

- Gravitational Potential Energy is energy stored due to an object’s position above the Earth’s surface

- PE = mgh
- m is the mass of an object, g is the acceleration due to gravity, h is the height above the Earth
- Standard units – kg m2/s2 or Joules (J)

- A 65 kg rock climber climbs a cliff. What is the climber’s potential energy when she is 35 m above the base of the cliff?
- m=65 kg, h=35m, g=9.8 m/s2
- PE = mgh = (65kg)( 9.8 m/s2)(35m) = 22295 J

- What is the mass of a hiker 200 m above the ground if her GPE is 117600 J?

- Find the height of a baseball with a mass of .15kg and has a GPE of 73.5 J?

- a moving skateboard,
- a rock at the edge of a cliff,
- an unconnected battery,
- a baseball being pitched,
- a gallon of gas,
- a stretched rubber band,
- a moving car,
- a person climbing stairs
- a pizza

- What happens when you turn on a lightbulb?
- What happens to the lightbulb if you leave it on for a long time?

- Mechanical energy is the total amount of kinetic and potential energy in a system.
- ME = KE + PE

- Law of Conservation of Energy – energy can not be created or destroyed, only transformed.