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ENERGY

ENERGY. Image source: http://www.greenearthproject.com/Forms2.html. POTENTIAL ENERGY. Gravitational Potential Energy. Depends on height. Elastic Potential Energy. Associated with objects that can be stretched or compressed. CHEMICAL ENERGY. energy required to bond atoms together.

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ENERGY

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  1. ENERGY

  2. Image source: http://www.greenearthproject.com/Forms2.html

  3. POTENTIAL ENERGY

  4. Gravitational Potential Energy Depends on height

  5. Elastic PotentialEnergy Associated with objects that can be stretched or compressed

  6. CHEMICAL ENERGY energyrequired to bond atoms together

  7. NUCLEAR ENERGY released in the form of light and heat energy as the nucleus splits Image source: http://typesofalternativeenergy.com/

  8. Most concentrated form of energy > 50,000 DEGREES CELSIUS

  9. KINETIC ENERGY

  10. Movement of turbines Image source: http://www.entergy.apogee.net/ Image source: http://technicalstudies.youngester.com MECHANICALENERGY energy associated with motion

  11. Moving electric charges Internal motion of atoms

  12. Heat energy causes changes in the temperature and phase (solid, liquid, gas) of any form of matter

  13. http://www.youtube.com/watch?v=RD_54Cq_UMM Changes in Energy Video ENERGY TRANSFORMATIONS

  14. http://172.25.31.139/index.asp?ResourceString=MSMC/Physics/ Media Server Online: Potential and Kinetic Energy

  15. Energy cannot be created nor destroyed. Energy is converted from one form to another.

  16. CONSERVATION OF ENERGY 1-11 Lecture 11_ Work - Kinetic Ener.mp4

  17. Law of CONSERVATION OF ENERGY “Energy cannot be creatednor destroyed. Energy is converted from one form to another.”

  18. maxPE = maxKE

  19. Videos on KE and Pe • Kinetic & Potential Energy

  20. What you know • An object that has energy can do work. • Work is done when energy is transferred from one object to another or changed from one form to another.

  21. WORK put in can increase can do K.E. P.E.

  22. WORK AND ENERGY • 1.max PE = max KE • 2. Work = Energy • Work = PE gained = KE • Work = KE

  23. ENERGY

  24. Units: Energy and Work = joules (J) = Newton-meter (Nm) Mass = kilograms (kg) Weight = newtons (N) Gravity constant = 9.8m/sec/sec ~ 10 m/sec/sec Velocity = m/s Height = meters (m) 1km = 1000m 1kg= 1000g 1hr= 3,600sec

  25. Weight Vs. Mass http://www.youtube.com/watch?v=grWG_U4sgS8&feature=related

  26. Weight and Mass Weight is a measure of the force of gravity on an object Weight = Mass x acceleration due to gravity w= mg

  27. POTENTIAL ENERGY

  28. ENERGY A BODY HAS BECAUSE OF ITS POSITION OR CONDITION P.E.= Ep = mgh G.P.E. = weight x height

  29. mv2 KE 2 KINETIC ENERGY (Ek) = ½ mv2 = Kinetic energy Ek or k.e. is the energy that an object has because it is moving

  30. Potential Energy: PE or Ep or GPE = Weight x height (P.E. = w x h) weight = m x g or = mass x gravity x height (PE = m x g x h) Kinetic Energy: KE or Ek = ½ Mass x Velocity2 (K.E.= 1/2m xv2) or = m x v2 2

  31. STEPS IN PROBLEM SOLVING • STEP 1. Write the formula • STEP 2. Substitute given numbers and units • STEP 3. Solve for the unknown.

  32. EXAMPLE What is the p.e. of a book of mass 1200 g, resting on a shelf 2 m above the ground? p.e. = mgh p.e. = 1.2kg x 10m/s/s x 2m p.e. = 12.0 N x 2 m p.e. = 24 N-meter or Joules

  33. SAMPLE PROBLEM: A hiker weighing 680 N climbs 40 m up a hill. Calculate the gravitational potential energy gained at the top of the climb.

  34. Ep= wxh Ep = 680 N x 40m = 27,200 N-m or 27.2 KJ

  35. Calculate the p.e. of a 40 kg iron bar raised 1 m. (g = 10m/s/s) identify the tricky part of this next Q: 2. Calculate the p.e. of a 65,000 g boulder resting at 22 m above the road. Try this one: 3. How high is a .2 kg jar if it has 3J of p.e.?

  36. ANSWERS 1. Calculate the p.e. of a 40 kg iron bar raised 1 m. 400 N-m or 400J 2. Calculate the p.e. of a 65,000 g boulder resting at 22 m above the road. 14,300 N-m or 14.3 KJ 3. How high is a .2 kg jar if it has 3J of p.e.? 1.5 m

  37. What is the Ek of an arrow with a mass of 25 g traveling at 25m/s?

  38. What is the Ek of an arrow with a mass of 25 gm traveling at 25m/s? Answer: k.e. = ½ mv2 = ½ x .025kg x (25m/s)2 = ½ x 0.025kg x 625m/s = (0.5) 15.625 = 7.8125 Nm but 1 Nm = 1J = 7.8125 J

  39. SUMMARY OF CONCEPTS: • If h is doubled, the GPE is doubled. • If H is tripled, the GPE is also tripled. • If speed (velocity) is doubled (2x), the Kinetic Energy increases (4x or 22). • If speed (velocity) is tripled (3X), the KE increases9x or 32. • The GPE at the top changes to KE at the bottom. GPE = w x h or GPE = mgh

  40. KINETIC ENERGY • The greater the speed the greater the • k.e. of the object • The greater the mass of a moving • object, the greater the k.e. of the • object

  41. POTENTIAL ENERGY Ep or p.e. is the potential energy an object has because of its height. “The higher an object is lifted, the greater its p.e.” “The greater the mass of an object the greater its p.e.” the gain in p.e. = work doneEp = W

  42. Putting these formulae together: Gain in Potential energy= work done lifting Ep = W = lifting force x distance lifted (height)Ep = F x d (h) = weight force x distance lifted Ep = Fg x d (h) (g = 10N/kg) = mass of object x g x distance liftedEp = mgh

  43. Video clip \\server14\stares$\Middle School\Science\Grade Levels\Grade 8\8.2 Transformations\Conservation of Energy\1-11 Lecture 11_ Work - Kinetic Ener.mp4 Conservation of Energy

  44. AMUSEMENT PARK PHYSICS Applying potential and kinetic energy

  45. Height (h in meters/m)

  46. PE = m g h E k = ½ m v2

  47. ROLLER COASTERS http://www.funderstanding.com/K12/coaster/ http://dsc.discovery.com/convergence/coasters/interactive/interactive.html

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