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I.P.C. 6 A

I.P.C. 6 A. Describe the law of conservation of energy. (This law includes calculation of G.P.E.). Conservation of Energy

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I.P.C. 6 A

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  1. I.P.C. 6 A Describe the law of conservation of energy. (This law includes calculation of G.P.E.)

  2. Conservation of Energy Energy in a system may take on various forms (e.g. kinetic, potential, heat, light). The law of conservation of energy states that energy may neither be created nor destroyed. Therefore the sum of all the energies in the system is a constant. Example: A roller coaster on top of a hill has potential energy. When the roller coaster rolls downward the PE is converted into Kinetic Energy.

  3. The sun or solar energy is the source of energy for all living organisms. • In photosynthesis, plants convert solar energy into stored glucose (sugar) energy. • This energy is transferred to animals through the food chain

  4. Mechanical Energy Electrical Energy Heat Energy APPLYING THE CONSERVATION OF ENERGY (Energy can be converted from one form of energy to another, but energy never just appears or disappears.)

  5. Which of the following is an example of solar energy being converted into chemical energy? TAKS 2004 • Plants producing sugar during the day • Water evaporating and condensing in the water cycle • The sun unevenly heating Earth’s surface • Lava erupting from volcanoes for many days Answer: A, because plants use sunlight to make sugar which is a stored chemical energy for them to use.

  6. Why is the sum of the products’ energy in this reaction less than the sum of the reactant’s energy? TAKS 2004 • Energy is given off as heat • The products absorb available energy • Energy is trapped in the reactants • The reactants’ energy is less than the melting point of glucose Answer: A, because energy is not lost or gained but can be converted to other forms. Heat or Thermal Energy is one common conversion.

  7. An inventor claims to have created an internal combustion that converts 100kJ of chemical energy from diesal fuel into 140kJ of mechanical energy. This claim violates the law of conservation of: • momentum • inertia • energy • mass TAKS 2004 Answer: C, because by changing 100kJ of energy into 140kJ you have created energy which violates the law of conservation of energy.

  8. Fuel cells powered by plankton from the seabed can be used to operate instruments that monitor ocean currents and water temperature. These fuel cells get their energy by converting – • chemical energy to electrical energy • electrical energy to mechanical energy • hydroelectric energy to geothermal energy • mechanical energy to chemical energy Answer: A, because plankton (plants) convert sunlight to glucose (chemical energy) which is converted to electrical energy to power fuel cells.

  9. YOUR TURN GET OUT SCRAP PAPER AND YOUR FORMULA CHART

  10. Formulas Constants, Symbols and Units Formula Chart Today we will work with the kinetic energy and gravitational potential energy formulas. Find them on your Formula Chart. K.E. and G.P.E.

  11. KINETIC ENERGY Kinetic energy is the energy of motion. An object which has motion - whether it be vertical or horizontal motion - has kinetic energy. There are many forms of kinetic energy - vibrational (the energy due to vibrational motion), rotational (the energy due to rotational motion), and translational (the energy due to motion from one location to another).

  12. What is the kinetic energy of a 625-kg roller coaster car that is moving with a speed of 18.3 m/s. K.E. = (625) x (18.3)2 2 = 104653.12 J Answer: D 1.05 x 105 Joules

  13. GRAVITY POTENTIAL ENERGY Potential energy is energy that is stored in an object. (A stretched rubber band has potential energy. When you release the stretch the potential energy is converted to kinetic energy and the rubber band flies through the air. (Kinetic energy is energy of motion) Notice the potential energy was changed to kinetic energy but no energy was lost or gained. Gravitational potential energy is the energy stored in an object as the result of its vertical position or height. (Example a boulder on top of a mountain)

  14. Formulas Gravity = 9.8 m/s2 Constants, Symbols and Units Formula Chart In GPE problems we need to know what force gravity exerts. Where do we get the information?

  15. 59,900 J 64,600 J 93,100 J 121,500 J What is the potential energy of the rock? TAKS 2003

  16. 59,900 J 64,600 J 93,100 J 121,500 J What is the potential energy of the rock? TAKS 2003 P.E. = (95)(9.8)(100)

  17. 19 J 39 J 59 J 79 J What is the approximate difference in gravitational potential energy of the two shaded boxes? TAKS 2005-06

  18. 19 J 39 J 59 J 79 J P.E. = (2)(9.8)(3.0)=58.8 P.E. = (2)(9.8)(1.0)=19.6 What is the approximate difference in gravitational potential energy of the two shaded boxes? TAKS 2005-06 58.8 – 19.6 = 39.2 J

  19. FOLDABLE TIME Make a Foldable for Gravitational Potential Energy and Kinetic Energy

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