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Understanding Energy: Forms, Equations, and Work

Learn about different forms of energy, equations for kinetic and potential energy, and the concept of work in physics. Explore the law of conservation of energy and practical calculations.

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Understanding Energy: Forms, Equations, and Work

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  1. Unit 3 PhysicsEnergy

  2. Energy • The ability to do WORK… • Measured in JOULES (J)

  3. Law of Conservation of Energy • energy cannot be created or destroyed only transferred from one form to another Electric  Light Chemical  Mechanical

  4. 2 forms of mechanical energy 1. Kinetic energy (KE) -energy due to motion ex: anything moving KE = ½ mv2 (J) (kg)(m/s)2 (N) (m)

  5. Calculate KE A 1216kg car traveling at 10m/sec. KE = ½ mv2 m = 1216kg v = 10m/sec KE = ½ (1216kg)(10m/sec)2 KE = ½ (1216kg)(100(m/s)2 ) KE = 60,800J

  6. 2. Potential energy (PE) -energy due to position or condition ex: book high on a shelf stretched rubber band wound up clock -the only PE we calculate is gravitational potential PE = m g h (J) (kg)(m/s2)(m) (N) (m)

  7. Calculate PE m = g = 500N PE = m g h h = 100m PE = (500N) (100m) PE = 50,000J

  8. Energy 7 Types of Energy • 1. Light - energy traveling in waves • 2. Mechanical - energy of lifting, bending, etc… (work) • 3. Thermal - molecular motion

  9. 5. Nuclear – energy in atomic nuclei (holds protons & neutrons together) • 7. Chemical - energy stored in chemical bonds 4. Electrical – moving electrons 6. Sound - vibrations

  10. Work – Energy Theorem • All work is energy, but not all energy is work

  11. Work -transfer of energy through motion *Object must move in direction force applied!

  12. Work • Equation: W = Fd W = work F = force d = distance • Work is measured in Joules (J) J = N m *Joule is always (N)(m), never (N)(cm)!!

  13. A teacher pushed a 10kg desk across a floor for a distance of 5m. She exerted a horizontal force of 20N. How much work was done? F = 20N d = 5m W = Fd W = (20N)(5m) W = 100J

  14. A force of 10,000N is applied to a stationary wall. How much work performed on the wall? F = 10,000N d = 0m W = Fd W = (10,000N)(0m) W = 0J

  15. Check up: • Where does the pendulum have greatest PE? • Where does the pendulum have greatest KE? Greatest PE Greatest PE Greatest KE

  16. Check up: • Which of the 3 vehicles has the greatest KE? • Which car has the greatest KE?

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