Understanding Energy: Forms, Potential, Kinetic, and Applications

2. The Law of Conservation of Energy • Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes.

3. What is energy? • “the ability to do work” • The combination of energy and matter make up the universe: • Matter is substance, and energy is the mover of substance.

4. Energy is nature’s way of keeping score. We sense energy only when the score changes, either a transformation from one form of energy to another, or a transfer of energy from one point to another.

5. Kinetic Energy Potential Energy Elastic Potential Energy Gravitation Potential Energy Chemical Potential Energy How is all energy divided? All Energy

6. energy of position or energy in storage. Water behind a dam Hammer over head Food on the plate energy of motion, the form capable of doing work Flowing water A falling hammer Electrons regenerating ATP in a bio’l cell Potential Kinetic

7. PE = mgh • m = mass (kg) • h = height (m) • g = accel due to gravity • (9.8 m/s2)

8. Kinetic Energy • KE of an object depends upon two variables: • the mass (m) of the object • the speed (v) of the object.

9. What is Gravitational Potential Energy? • Potential energy due to an object’s position • P.E. = mass x height x gravity Don’t look down, Rover! Good boy!

10. Gravitational Potential Energy • GPE is the energy stored in an object as the result of its vertical position (i.e., height). • Amount of GPE is dependent on two variables: • the mass • the height

11. Calculating Gravitational Potential Energy GPE = mgh (rate an object falls due to gravity) g = 9.8m/sec2

12. What is Potential Energy? • Energy that is stored and waiting to be used later

13. What is Elastic Potential Energy? • Potential energy due compression or expansion of an elastic object. Notice the ball compressing and expanding

14. What is Chemical Potential Energy? • Potential energy stored within the chemical bonds of an object

15. What is Kinetic Energy? • Energy an object has due to its motion • K.E. = .5(mass x speed2)

16. 4 kg bowling ball at 10 m/s = .5 (4kg) (10m/s)2 = 200 J .25 kg baseball at 50 m/s = .5 (.25kg) (50 m/s)2 = 312 J KE = 1/2 m v2

17. Kinetic Energy The greater the mass or velocity of a moving object, the more kinetic energy it has.

18. Courtesy Jerry Ohlinger’s Movie Material Store Work is done when a force is exerted over a distance.

19. Work • is equal to the force that is exerted times the distance over which it is exerted. • W = F x d • The unit of work combines the unit of force (N) with the unit of distance (m) • Newton-meter (N-m) aka Joule.

20. You carry a 20 kg suitcase upstairs, a distance of 4m. How much work did you do? • W = F x d • F = ma • = (20 kg) (10m/s2) = 200 N • W = F x d • = (200 N) (4m) • = 800 J

21. Power • measures the rate of work done. • or the rate at which energy is expended. • Power is the amount of work done, divided by the time it takes to do it. • Power (watts) = work (joules) / time (sec) • P = W/t

22. Power • Since work performed equals energy expended, • Power (watts) = energy (joules) / time (sec) • The watt is defined as the expenditure of 1 joule of energy in 1 second. (75 watt light bulb consumes 75 J/sec)

23. Important formulas and units Quantity Definition Units Force mass x accel. newtons Work force x distance joules Energy power x time joules Power work / time watts

24. Ex. Problem on Power: • Your CD system, uses 250 watts of electrical power. • You play it for 3 hrs. How much energy used? About how much would it cost? If one kWh is $.08. • Energy (J) = power (watts) x time (sec) = (250w) (3hr) = 750 Whr = .75 kWh • The cost = 8 cents/ kWh x .75 kWh • = 6 cents

25. Power = work / time • . Two physics students, Will N. Andable and Ben Pumpiniron, are in the weightlifting room. Will lifts the 100-pound barbell over his head 10 times in one minute; Ben lifts the 100-pound barbell over his head 10 times in 10 seconds. Which student does the most work? Which student delivers the most power?

26. Mechanical Advantage • The number of times a machine multiplies your effort force. • Example: If you push on the handle of a car jack with a force of 30 lbs and the jack lifts a 3000 lb car, what is the jack’s mechanical advantage? • The jack multiplies your effort force by 100 times.

27. IMA – Ideal mechanical advantage. This is the number of times a machine is designed to multiply your effort force. It is based on measurements of the machine. Ignores friction AMA – Actual mechanical advantage This is the number of times the machine actually multiplies your effort force. AMA = resistance force/effort force. Includes the effects of friction There are 2 types of mechanical advantage. IMA is always greater than AMA.

28. Mechanical Advantage • Mechanical advantage is the ratio of output force divided by input force. If the output force is bigger than the input force, a machine has a mechanical advantage greater than one. • If a machine increases an input force of 10 pounds to an output force of 100 pounds, the machine has a mechanical advantage (MA) of 10. • In machines that increase distance instead of force, the MA is the ratio of the output distance and input distance. MA = output/input

29. Drawing Conclusions • Two divers of equal mass about to dive • Diver A has > Potential Energy than B • Compare divers positions • Which diver will hit water @ highest speed • What happens to energy when diver enters the water?

30. Diver A Fastest Diver B

31. 6 fundamental forms of energy • mechanical energy • Thermal (heat) energy • electromagnetic energy • electrical energy • nuclear energy • chemical energy

32. What is the source of our energy? • The source of practically all our energy is the Sun.

33. Energy due to a object’s motion (kinetic) or position (potential). The bowling ball has mechanical energy. When the ball strikes the pins, mechanical energy is transferred to the pins! What is Mechanical Energy?

34. Mechanical Energy Mechanical energy is the movement of machine parts. Mechanical energy comes from the motion (kinetic energy) and position (potential energy) of objects. EXAMPLES: Wind-up toys, grandfather clocks, and pogo sticks Wind power uses mechanical energy to help create electricity. Potential energy + Kinetic energy = Mechanical energy

35. Examples of Mechanical Energy

36. Light energy Includes energy from gamma rays, xrays, ultraviolet rays, visible light, infrared rays, microwave and radio bands What is ElectromagneticEnergy?

37. Energy caused by the movement of electrons Easily transported through power lines and converted into other forms of energy What is Electrical Energy?

38. Electrical Energy Electrical energy is the movement of electrons. Examples: Lightning and static electricity occur naturally. Science hasn't found a way to use natural forms of electrical energy. We use different energy sources to create electrical energy by using generators and turbines.

40. Energy that is available for release from chemical reactions. The chemical bonds in a matchstick store energy that is transformed into thermal energy when the match is struck. What is Chemical Energy?

41. Examples of Chemical Energy

42. Chemical Energy Chemical energy is the energy stored in the bonds of atoms and molecules. This a form of potential energy until the bonds are broken. Examples: Fossil fuels store chemical energy. Products that contain chemical energy include: TNT, baking soda, and a match. Biomass, petroleum, natural gas, propane and coal are examples of stored chemical energy.

43. Heat energy The heat energy of an object determines how active its atoms are. A hot object is one whose atoms and molecules are excited and show rapid movement. A cooler object's molecules and atoms will show lessmovement. What is Thermal Energy?

44. Thermal Energy Thermal energy is the internal energy in substances - the vibration and movement of atoms and molecules within substance. Thermal energy is created in the movement of atoms. EXAMPLES: Boiling water, burning wood, and rubbing your hands together really fast. Geothermal and passive solar are sources of heat energy.

45. Nuclear Energy Nuclear energy is the energy stored in the nucleus of an atom. Nuclear energy is unusual in that it can give off energy in the form of light or heat, but it is the change in the atom's makeup that produces the energy.

46. Nuclear Energy All power plants convert heat into electricity using steam. At nuclear power plants, the heat to make the steam is created when atoms split- fission. Fission takes place when the nucleus of a heavy atom like plutonium or uranium is split into two when struck by a neutron. This releases more neutrons which repeat the process and releases more nuclear energy (heat). This heat boils water and creates steam that turns a turbine. As a turbine spins, the generator turns and its magnetic field produces electricity that goes to your house.

48. QUIZ TIME! What type of energy cooks food in a microwave oven? ELECTROMAGNETIC ENERGY What type of energy is the spinning plate inside of a microwave oven? MECHANICAL ENERGY

49. QUIZ TIME! Electrical energy is transported to your house through power lines. When you plug an electric fan to a power outlet, electrical energy is transform into what type of energy? MECHANICAL ENERGY

50. QUIZ TIME! What energy transformation occurs when an electric lamp is turned on? ELECTRICAL ENERGY  ELECTROMAGNETIC ENERGY