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Energy & Conservation

Energy & Conservation. Chapter 11 Section 11.1 & 11.2. Learning Objectives. Distinguish between kinetic and potential energy and calculate by formulas. Recognize the factors affecting kinetic (speed and mass) and gravitational potential (mass, height and gravity)energies.

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Energy & Conservation

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  1. Energy & Conservation Chapter 11 Section 11.1 & 11.2

  2. Learning Objectives • Distinguish between kinetic and potential energy and calculate by formulas. • Recognize the factors affecting kinetic (speed and mass) and gravitational potential (mass, height and gravity)energies. • State the law of conservation of energy • Describe the transformation of energy from one to another (using example free fall)

  3. Section 11.1 Kinetic Energy Kinetic Energy exists whenever an object which has mass is in motion with some velocity. KE = (1/2)mv2 The kinetic energy is proportional to the object’s mass. Units are Joules A 7.26-kg ball kinetic energy more or 0.148-kg baseball with the same velocity….?

  4. Section 11.1 Gravitational Potential Energy • Potential energy exists whenever an object which has mass has a position within a force field. Gravitational Potential EnergyPE = mgh g is the acceleration due to gravity. Gravitational potential energy Units : joules

  5. Phts Simulations

  6. Transformation of K.E & P.E • When a ball is thrown upward.

  7. Transformation of K.E & P.E • When a ball is dropped downward(taking reference line upward)

  8. Section 11.2 Law of Conservation of Energy • The law of conservation of energy states that in a closed system energy is conserved. (Energy changes from one form to another while the total energy of the system remains constant.

  9. Section Mechanical Energy 11.2 • The sum of the kinetic energy and gravitational potential energy of a system is called mechanical energy. Mechanical Energy ME = KE+PE • The mechanical energy of a system is equal to the sum of the kinetic energy and potential energy if no other forms of energy are present.

  10. Section Conservation of Energy 11.2 • A ball is falling down freely from height of 2m. Find its ME at three points. Click image to view the movie.

  11. Examples of ME conservation Skiing Pendulum

  12. Energy and Its Conservation CHAPTER11 Chapter Resources A Child Sliding Down a Playground Slide

  13. Energy and Its Conservation CHAPTER11 Chapter Assessment If a car is moving backward, what can we say about its kinetic energy? A.Kinetic energy is negative as it is moving backward. B. Kinetic energy is positive. C. The car does not possess kinetic energy. D. Kinetic energy of the car gets stored as gravitational potential energy.

  14. Energy and Its Conservation CHAPTER11 Solve Q1 Standardized Test Practice You lift a 4.5-kg box from the floor and place it on a shelf that is 1.5 m above the ground. How much energy did you use in lifting the box? A.9.0 J B.49 J C.11 J D.66 J

  15. Energy and Its Conservation CHAPTER11 Q2 Standardized Test Practice You move a 2.5-kg book from a shelf that is 1.2 m above the ground to a shelf that is 2.6 m above the ground. What is the change in the book’s potential energy? A. 1.4 J B. 25 J C.3.5 J D. 34 J

  16. Energy and Its Conservation CHAPTER11 Q3 Standardized Test Practice You drop a 6.0×10−2 −kg ball from a height of 1.0 m above a hard, flat surface. The ball strikes the surface and loses 0.14 J of its energy. It then bounces back upward. How much kinetic energy does the ball have just after it bounces off the flat surface? A.0.20 J B.0.59 J C.0.45 J D.0.73 J

  17. Problem solving question…… Worksheet • Online Quiz ……….. PLATO • Class Activity………… PLAO

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