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Energy

Energy. Energy and Work. Energy – the ability to do work Work is a transfer of energy Energy is also measured in Joules. Kinetic Energy. Kinetic energy – energy of an object’s motion Depends on mass and speed Equation: Kinetic energy (KE) = ½ mv 2. Kinetic Energy Example.

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Energy

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  1. Energy

  2. Energy and Work • Energy – the ability to do work • Work is a transfer of energy • Energy is also measured in Joules

  3. Kinetic Energy • Kinetic energy – energy of an object’s motion • Depends on mass and speed • Equation: • Kinetic energy (KE) = ½ mv2

  4. Kinetic Energy Example • A 0.10 kg bird is flying at a constant speed of 8 m/s. What is the bird’s kinetic energy? m = 0.10 kg KE = ½ (0.10)(82) v = 8 m/s KE = ½ (0.10)(64) KE = ? KE = ½ (6.4) KE = 3.2 J

  5. Potential Energy • Potential energy – stored energy • Energy of an object that is not moving • Gravitational potential energy – depends on an object’s height and weight (mass and acceleration of gravity) • Gravitational potential energy equation • Potential energy (PE) = mgh • mg = weight • m = mass • g = gravity (9.8 m/s2) • h = height

  6. Potential Energy Example • A diver with a mass of 50.0 kg is at the top of a 10.0 m high diving board. What is her potential energy relative to the ground? m = 50.0 kg PE = (50.0 kg)(9.8 m/s2)(10.0 m) g = 9.8 m/s2 PE = 4900 J h = 10.0 m PE = ? If the diver stands on the ground instead of the diving board, what is his/her potential energy relative to the ground? Zero because the height from the ground is zero

  7. Potential Energy Cont’d… • Elastic potential energy – energy of a stationary object that is being stretched or compressed • Ex: rubber bands, springs

  8. Forms of Energy • Mechanical Energy – motion and position of everyday objects • Sum of KE and PE • Thermal Energy – PE and KE of atoms of an object • Related to heat • Chemical Energy – energy stored in chemical bonds • Electrical Energy – associated with electrical charges • Electromagnetic Energy – form of energy that travels through space in the form of waves • Ex: x-rays, UV waves • Nuclear Energy – stored in an atom’s nucleus

  9. Energy Conversion • Energy can change from one form to another • Ex: light bulbs • Electrical energy can be converted to thermal energy

  10. Conservation of Energy • Law of Conservation of Energy – energy cannot be created nor destroyed • It can only change forms!

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