Energy – Part II

1. Energy – Part II

2. Forms of Energy • Mechanical • Electrical • Chemical • Nuclear • Thermal/Geothermal • Sound • Seismic • Radiant

3. Kinetic and Potential Energies Combined • Mechanical Energy – The sum of potential energy and kinetic energy in a system of objects. • The energy an object has because of a combination of the following: The movement of its parts (kinetic energy) The position of its parts (potential energy)

4. Kinetic and Potential Energies Combined • Mechanical Energy – How does the wind turbine shown in the picture have mechanical energy? • Kinetic Energy – the rotating blade • Gravitational Potential Energy – distance from Earth’s surface

5. Wrecking Ball

6. Kinetic and Potential Energies Combined • Thermal Energy – The sum of the kinetic energy and potential energy of the particles that make up an object • Cannot always be seen. • Individual vibrate back and forth in place, giving them . • The particles also have because of the between particles and the of the particles. particles kinetic energy potential energy distance charge

7. Kinetic and Potential Energies Combined • The particles that make up the wind turbine have thermal energy.

8. Kinetic and Potential Energies Combined • The particles in Earth’s interior contain great amounts of • This type of energy is called thermal energy geothermal energy Geothermal energy plants convert thermal energy of the particles deep inside Earth to electric energy.

9. Kinetic Energy • Anything in motion has kinetic energy, including: • Large objects that you can see • Small particles that you cannot see (molecules, ions, atoms, and electrons) • Electric Energy – The energy that an electric current carries is a form of kinetic energy. • move around the nucleus of an and they can move from one atom to another. • When move, they have and create an Electrons atom kinetic energy electrons electric current

10. Kinetic Energy • Electric Energy – the blades of wind turbines rotate and turn a generator that changes the of the moving blades into kinetic energy electric energy

11. Potential Energy • Potential energy – stored energy that depends on: • Position or shape of an object. • Most electric energy (a type of kinetic) comes from fossil fuels such as • The atoms that make up fossil fuels are joined by Chemical Energy petroleum, natural gas, and coal. chemical bonds

12. Potential Energy • Chemical Energy – energy that is stored in and released from the bonds between atoms. • When fossil fuels burn, the between atoms that make up the fossil fuel . • When this happens, transforms into chemical bonds break apart chemical energy thermal energy

13. Potential Energy • Nuclear Energy – energy stored in and released from the nucleus of an atom. • Majority of energy on Earth comes from • and release nuclear energy. • Nuclear Fusion – • Nuclear Fission - the Sun nuclear fission Nuclear fusion A process that occurs in the sun which joins the nuclei of atomsand releases large amounts of energy. Nuclear energy plants on Earth break apart the nucleiof certain atoms.

14. Energy from Waves • Wave – a disturbance that carries energy from one place to another. • Waves move , NOT matter. energy WAVELENGTH CREST AMPLITUDE TROUGH

15. Energy from Waves • Sound Energy – the form of energy associated with the vibration or disturbance of matter • Some animals emit sound waves to find their prey. • For example: Bats – the amount of time it takes sound waves to travel to their prey and echo back tells the bat the location of the prey it’s hunting.

16. Energy from Waves • Seismic Energy – is the energy transferred by waves moving through the ground. • Earthquake’s occur when Earth’s suddenly position. • The of plate movement is carried through the ground by tectonic plates shift kinetic energy seismic waves

17. Energy from Waves • Radiant Energy – the energy carried by electromagnetic waves. • Electromagnetic waves – electric and magnetic waves that move perpendicular to each other. • Can travel through solids, liquids, gasses and vacuums.

18. Electromagnetic spectrum – the range of all possible frequencies of electromagnetic radiation. • The relationship between energy and wavelength: • The the wavelength the the energy. • The the wavelength the the energy. • The wave with the highest frequency is: • The wave with the lowest frequency is: shorter greater longer weaker gamma rays radio rays

20. Radio waves, light waves, and microwaves are all electromagnetic waves.

21. What’s the difference? • What is the difference between an energy TRANSFER and an energy TRANSFORMATION? • Energy Transfer – • Energy Transformation - When energy moves from one object to another without changing its form When one form of energy is converted to another form of energy.

22. Energy Transfers and Transformations • In every energy transfer and transformation some energy is transformed into thermal energy. • In every transformation such as electric to sound there is always thermal energy being transferred to surroundings.

23. Transfer or Transformation?

24. Transfer or Transformation?

25. Plants and The Body • Plants carry out a process called • During photosynthesis the plant absorbs from the sun and it into • The is stored in the plant. photosynthesis radiant energy transforms chemical energy chemical energy

27. Energy and Work • Work – the transfer of energy that occurs when a force makes an object move in the direction of the force. • Force- push or pull on an object • For example: The student does work on the drums when he lifts them. Once the drums are in place, no work is being done.

28. Work • Work is done only while the force is moving the object. • Work also depends on: • Joules – the unit of energy and work *Named After: James Prescott Joule – conducted experiments measuring the amount of work needed to create a given amount of heat. The distance an object moves during the time the force is applied.

29. Calculating Work Work = Force x distance

30. Sample Problem 1 • A student lifts a bag from the floor to his shoulder 1.2 meters above the floor, using a force of 50N. How much work does the student do on the bag?

31. Sample Problem 2 • Nicole lifts a flower pot onto a shelf 3 meters high, using a force of 30N. How much work is done to place the flower pot onto the shelf?

32. Energy and Heat • In every energy transformation and every energy transfer, some energy is transformed into thermal energy. • Thermal energy – the sum of kinetic and potential energy of the particles that make up an object. (Example: Friction) • When thermal energy is moving from a region of higher temperature to a region of lower temperature it is called heat. • Scientists sometimes call this heat because waste energy it is not easily used to do useful work.

33. Machines • Machines transfer • Simple Machines – machines that do work using one movement. • Simple machines do not change the amount of required to do a task; they only change the mechanical energy work way work is done

34. Simple Machines • Inclined plane- a flat, sloped surface. • Screw – an inclined plane wrapped around a cylinder.

35. Simple Machines • Wedge – an inclined plane that moves • Lever – a simple machine that pivots around a fixed point.

36. Simple Machines • Wheel and Axle – a shaft attached to a wheel of a larger diameter so that both rotate together. • Pulley – a grooved wheel with a rope or cable wrapped around it.

37. Complex Machines • Complex Machines – two or more simple machines working together.

38. Machines and Work • The work you do on a machine is called the • The work the machine does on an object is the • Machines make work easier by changing the the object moves or the required to do work on an object *remember – work is the product of force and distance. input work. output work. distance force

39. Efficiency • Efficiency - the ratio of output work to input work. • We express efficiency by • Efficiency equation: Efficiency is a measure of how much work put into the machine is changed into useful output work using a percentage. x 100 x 100

40. Efficiency NEVER 100% • The efficiency of a machine is • Some work is always transformed into because of • How could we improve efficiency of a machine? wasted thermal energy friction Reduce the wasted thermal energy by reducing friction. We could reduce friction by oiling the different parts of the machine.

41. Newton’s Laws and Simple Machines • Recall and define each of Newton’s Laws of Motion • How could we relate these laws to machines? 1st Law – an object in motion will stay in motion and an object at rest will stay at rest unless acted on by an unbalanced force. 2nd Law – the acceleration of an object is equal to the object’s net force divided by the objects mass. 3rd Law – every action has an equal and opposite reaction.

42. Newton’s 1st Law and Machines • Newton’s 1st Law tells us that the motion of an object changes when the forces that act on the object are • When you pull a hammer handle, the claws of the hammer apply a force on the nail. The hammer is acting as an that causes the nail to go from to . unbalanced. unbalanced force rest motion

43. Newton’s 2nd Law of Motion • Newton’s 2nd Law gives us the relationship between • Again, using the hammer as a lever applies to Newton’s 2nd Law because the more you apply to the hammer to remove the nail the quicker the nail will out of the piece of wood. force, mass and acceleration force move (accelerate)

44. Newton’s 3rd Law of Motion • Newton’s 3rd Law says that if one object applies a force on a second object, the second object will apply an equal force in the opposite direction. • For example, when you have a hammer being used as a to pull out a nail, you apply force on the hammer. The hammer applies • This is an lever an equal force in the opposite direction (back on you). action-reaction force