TAKS Objective 5

1. TAKS Objective 5  Motion , Forces and Energy

2. Energy Is defined as the Ability to do Work Energy has Two Types:

3. Kinetic Energy KE = ½ m v 2 Ex: A moving car has the ability to do work on the light pole if it hits it.

4. Potential Energy 2 possibilities Gravitational PE -Object lifted to some height Elastic PE - A stretched or compressed object )(springs

5. Gravitational Potential Energy or Will it fall? GPE = m g h m is the mass of the object in Kg, g is the acceleration due to gravity which is 9.8 m/s2 on earth and h is the height in meters

6. Use the formula page! PE = mgh 41 What is the potential energy of the rock? A 59,900 joules B 64,600 joules C 93,100 joules D 121,600 joules

7. Law of Conservation of Energy Energy can change forms, but is never created nor destroyed Loss in one form = gain in an another form A falling object speeds up as it falls to the ground; PE decreases as KE increases. The KE it has at impact = the PE it had before it fell.

8. Example: A falling object speeds up as it falls to the ground; PE decreases as KE increases, the KE it has at impact with the ground is equal to the PE it had before it fell

9. Energy can be conserved in Non-Mechanical forms The chemical energy in a battery transforms into electrical energy Any reaction where more energy is given off than is used to start it is Exogonic An Endogonic reaction absorbs energy and causes cooling

10. Electrical Energy - Moving electrons in a path is electricity Electrical Potential Difference (v) is measured in Volts The rate of moving electric charges, Electric Current (I), is measured in Amperes Resistance or opposition to the movement of the energy is called Resistance (R).

11. Circuits – 2 types Series circuits are the most simple. One (1) path for the current to travel. Contains an energy source, a path, and a load (something for it to do, like a lamp)

12. Circuits – 2 types Parallel circuits provide more than one path for the current to travel. Most circuits are parallel, since if one lamp goes out, the others can stay lit.

14. USE THE FORMULA SHEET!! What is the current in a copper wire that has a resistance of 2 ohms and is connected to a 9 volt electrical source? A. 0.22 amp B. 4.5 amps C. 11.0 amps D. 18.0 amps

15. Thermal Energy A body contains internal KE due to the motion of its atoms ( they are constantly wiggling and jiggling) Thermal Energy is the total internal KE of a body Temperature is the average KE of a body

16. Heat- Transfer of Thermal Energy 1. Conduction-direct contact, a pot heating on a stove 2. Convection- heating by circulating fluids, heating from a fireplace And. . .

17. 3. Radiation – Transfer of Electromagnetic (E.M.) Energy Objects are heated when exposed to infrared radiation The suns heats the earth by sending infrared radiation along with other forms of E.M. energy 93,000,000 miles through empty space

18. Heat moves by conduction in solids since the particles are close together and vibrate. . . 43 Heat convection occurs in gases and liquids. Heat convection does not occur in solids because solids are unable to — A absorb heat by vibrating B transfer heat by fluid motion C emit radiation by reflecting light D exchange heat by direct contact

19. 2 The primary way liquids and gases transmit heat is by the process of — F reflection G conduction H radiation J convection

20. F improve emission of infrared radiation G reduce the heat loss by convection currents H improve absorption of infrared radiation J reduce the heater’s conducting properties

21. Nuclear Reactions Fusion occurs when two atoms combine to form a new element. The sun produces all of its energy through fusion. Two hydrogen atoms combine to form a Helium atom from the great gravitational forces and pressure in the sun’s core

22. Nuclear Reactions - Fission Fission is the splitting of nucleii of large atoms such as Uranium and Plutonium Produces large amounts of infrared radiation and other forms of E.M. Energy such as Gamma Rays Currently, it is the main form of Atomic Energy on Earth

23. Radiant Energy or Electromagnetic Energy (EM) All radiant energy travels at 3.0 x 108 m/sec in space Velocity of a wave = wavelength x frequency Visible light is just one type of EM Energy

24. Electromagnetic Spectrum Radiation comes in the form of vibrating or “throbbing bundles of energy” called photons The frequency of the vibrating electric charges determines which type and how much energy will be given off

25. The entire E.M. Spectrum in order from lowest to highest frequency Radio waves: AM and FM Microwaves: cooking Infrared: heat Visible: (ROYGBV) Ultraviolet: tanning Xrays: medical Gamma:

26. Waves - Energy carried by rhythmic disturbances in space Two types: 1. E.M. radiation move through empty space 2. Mechanical require a medium (air or water) for movement

27. All waves have similar properties Frequency- the number of vibrations per second or the speed of the movement of the vibrating particles Amplitude – the size of the movement of the vibrating particles Both are controlled by the disturbance that created the waves

28. Velocity of all waves - v=f ? f-frequency and ? is wavelength (distance between identical points on two consecutive waves) Reflection- bounce off barriers in regular ways Refraction- waves can change direction when speed changes

29. And the answer is? 38 At 0°C sound travels through air at a speed of 330 m/s. If a sound wave is produced with a wavelength of 0.10 m, what is the wave’s frequency? F 0.0033 Hz G 33 Hz H 330 Hz J 3300 Hz

30. Transverse Waves In Transverse Waves particles vibrate at right angles to the direction the wave travels. Ex. E. M. Waves, waves on a slinky or rope coil, ocean waves

31. Waves - 2 Types

32. Longitudinal or Compress ional Waves Vibrating particles move back and forth along the direction of the wave velocity Parts consist of compressions and rarefactions Ex. Sound Waves

33. Sound Waves are Compressional Sound is produced when a compression is made. It requires a producer and a medium to travel through. The more elastic the object, the faster sound travels.

34. Sound acts like other waves Echoes are reflected sound waves Sonar uses echoes to judge distance to obstructions Human hearing is 20-20,000 Hz, below 10 Hz is infrasonic, and above 20,000 Hz is ultrasonic.

35. Sound Waves move through matter not through empty space. 32 One tuning fork is struck and placed next to an identical fork. The two forks do not touch. The second tuning fork starts to vibrate because of — F interference G the Doppler effect H resonance J standing waves

36. Forces and Motion Forces can create changes in motion (acceleration) Deceleration is negative acceleration

37. Motion can be described simply Motion is a change in an object’s position Average velocity (speed) is the change of position of an object over time

38. Velocity Graphs V = distance  time Velocity (v) is the slope (rise over run) of a position (d) vs. time (t) graph

40. Acceleration Graphs Acceleration (a) is the slope of a velocity (v) vs. time (t) graph Plotted on a distance vs. time graph, acceleration is an exponential curve

41. Acceleration is a change in an objects velocity (speed or direction) When an object’s speed changes over time it is accelerating (or decelerating) A = vfinal – vinitial time Units for acceleration m/s/s or m/s2

42. Forces A pull or push (or lift) that can cause an object to start moving, stop moving or change direction. 1665 Isaac Newton began to wonder why an apple falls down to the Earth. Concluded that the force that pulls an apple to the ground is the same force that helps keep the moon in orbit.1665 Isaac Newton began to wonder why an apple falls down to the Earth. Concluded that the force that pulls an apple to the ground is the same force that helps keep the moon in orbit.

43. Definition of a Force A Force is a push or a pull

44. Balanced Force A force that produces no change in an object’s motion because it is balanced by an equal, opposite force. If you were to add these forces they would = 0If you were to add these forces they would = 0

45. 4 The picture shows the position of a ball every 0.25 second on a photogram. Using a ruler, determine the velocity of the ball. F 3.5 cm/s G 10.5 cm/s H 14.0 cm/s J 28.0 cm/s

46. Since the version of the test you took has the picture smaller, we all got it wrong! The answer was H.

47. Unbalanced Forces Are forces that results in an object’s motion being changed. + Add together to equal greater force.Add together to equal greater force.

48. Friction A force that acts in a direction opposite to the motion of two surfaces in contact with each other.

49. Friction Friction causes an object to slow down and stop. Since the amount of energy stays constant, the energy becomes heat. Air resistance is an another example of friction. Lubricants or grease reduce friction.Air resistance is an another example of friction. Lubricants or grease reduce friction.

50. Newton’s 1st Law of Motion Object in motion stays in motion

51. Newton’s 1st Law of Motion And Objects at rest stay at rest

52. Newton’s 1st Law of Motion Until they are acted upon by unbalanced forces.

53. Inertia Tendency for an object to stay at rest or moving in a straight line at a constant speed. The mass (m measured in kg) of an object determines its inertia Inertia comes from the Latin word meaning lazy. Inertia comes from the Latin word meaning lazy.

54. Newton’s 2nd Law of Motion Force = Mass X Acceleration F=ma Weight (pull of gravity) is a commonly measured force, calculated by F=mg, g is the acceleration due to gravity 9.8 m/s2

55. Newton’s 2nd Law of Motion The greater the mass of an object, the greater the force required to change its motion.

56. Newton’s 2nd Law of Motion The greater the acceleration of an object, the greater the force required to change its motion.

57. A 0.2 N B 0.8 N C 1.5 N D 6.0 N

58. Newton’s 3rd Law of Motion For every action force there is an equal and opposite reaction force.

59. Newton’s 3rd Law of Motion All forces come in action-reaction pairs Ex: feet push backward on floor, the floor pushes forward on feet

60. 27 A ball moving at 30 m/s has a momentum of 15 kg·m/s. The mass of the ball is — A 45 kg B 15 kg C 2.0 kg D 0.5 kg

61. Work Work: using a force for a distance W = F x d The work done by forces on an object = changes in energy for that object. Work and Energy are measured in Joules 1 Joule=1 Newton • meter

62. 42 How much work is performed when a 50 kg crate is pushed 15 m with a force of 20 N? F 300 J G 750 J H 1,000 J J 15,000 J

63. Why use a machine? In an ideal (perfect) machine the work put into the machine (Win) = the work put out by that machine (Wout)

64. Machines make work easier The ideal mechanical advantage of a machine (IMA) of a machine is the number of times the output force is larger than the input force IMA=Fout/Fin A machine can only make this happen by moving the input force through a farther distance than the output force Fin • din=Fout • dout

65. 48 The diagram shows an electric motor lifting a 6 N block a distance of 3 m. The total amount of electrical energy used by the motor is 30 J. How much energy does the motor convert to heat? F 9 J G 12 J H 18 J J 21 J

67. Real Machines use Energy No real machine is 100 % efficient. i.e. none put out more work than is put in Efficiency of a machine is work output/work input X 100 % Eff = Wout X 100% Win

68. Machines use power Power: the rate at which energy is used (work is done) P=Work/time Power is measured in H.P. or watts 1 watt = 1 Joule 1 sec

69. A accelerated rapidly B remained motionless C decreased its velocity D gained momentum

70. 6 Types of simple machines Some Simple Machines: Inclined planes Screws Pulleys Wheel and axle Levers Wedge

71. Universal Law of Gravitation All objects in the universe attract each other by the force of gravity

72. Universal Law of Gravitation Gravity varies depending on two factors:

73. On Earth gravity = 9.8 m/s/s For every second that an object falls its speed increases by 9.8 m/s

74. Weight= Mass (m) X acceleration due to gravity (g) Weight Unit of mass = kg Unit of acceleration = m/s/s Unit of weight = Newton 1 Newton= about ¼ pound