2. TAKS Objective 5 Motion, Forces and Energy

3. Energy Is defined as the ability to do work Mechanical energy has two types : Kinetic (Energy of Motion) and Potential (Stored Energy)

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

5. Potential Energy 2 possibilities Gravitational PE - Object lifted to some height Elastic PE - A stretched or compressed object (spring or rubber band)

6. Gravitational Potential Energy or Wi ll it fall? GPE = mgh m is the mass of the object in kg, g is the acceleration due to gravity which is 9.8 m/s 2 on earth and h is the height in meters

7. 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 m = 95 kg g = 9.8 m/s 2 h = 100 m 95 kg x 9.8 m/s 2 x 100 = 93,100 joules C

8. Law of Conservation of Energy ENERGY cannot be created or destroyed, but can be changed from one form to another 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.

9. 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

10. Energy can be conserved in non-mechanical forms The chemical energy in a battery transforms into electrical energy Any reaction where more heat energy is given off than is used to start it is exothermic An endothermic reaction absorbs heat energy and causes cooling

11. Electrical Energy - Moving electrons in a path is electricity Potential energy (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) and is measured in Ohms.

12. 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)

13. 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. F. Q G. R H. S J. T 6.Which switches, if opened, will cause the light bulb to stop glowing? It is the only switch in series to both the battery and light.

15. 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 V = I R so, 9V = I x 2 ohms or 4.5 amps

16. 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

17. Heat- Transfer of Thermal Energy 1. Conduction-direct contact, a pot heating on a stove (solids) 2. Convection- heating by circulating fluids, (gas and liquid) heating from a fireplace And... Three forms of heating:

18. 3. Radiation – Transfer of Electromagnetic (E.M.) Energy The suns heats the earth by sending infrared radiation along with other forms of E.M. energy at a speed of 3.0 x 10 8 meters/second through empty space

19. 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 Solids do radiate heat to their surroundings

20. 2 The primary way liquids and gases transmit heat is by the process of — F reflection G conduction H radiation J convection Fluid heat movement is convection. Fluid motion occurs in liquids and gases.

21. 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 50 A solar heater uses energy from the sun to heat water. The heater’s panel is painted black to — Emission is giving off – we want to absorb: Not F Convection is movement of heat in fluid matter, heat loss would be from a solid exterior – Not G Painting a substance will not change its conductivity – That is a property of metals. It would have to be made of a different substance to change that: Not J

22. 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

23. 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

24. Radiant Energy or Electromagnetic Energy (EM) All radiant energy travels at 3.0 x 10 8 m/s in space ROYGBIVROYGBIV Visible light is just one type of EM energy

25. Electromagnetic Spectrum Radiation comes in the form of vibrating or “throbbing bundles of energy” called photons The direction of the vibrating electric charges determines which type and how much energy will be given off All of the forms of radiation given off by vibrating electric charges

26. The entire E.M. Spectrum in order from lowest to highest frequency Radio waves: AM and FM Microwaves: cooking Infrared waves: heat Visible light: (ROYGBIV) Ultraviolet: tanning X-rays: medical Gamma rays:

27. Waves - Energy carried by rhythmic disturbances Two types: 1. Radiation (electromagnetic waves) move through empty space 2. Mechanical waves require a medium (air, water or any type of matter) for movement

28. Waves - 2 Types

29. 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

30. Velocity of all waves - v=f λ F is frequency and λ 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

31. 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 Use the formula chart!!! f λ OR Velocity = f λ OR 330 m/s = f x 0.10 m J 3300 Hz

32. TRANSVERSE Waves In transverse waves particles vibrate at right angles to the direction the wave travels. Ex. electromagnetic waves, waves on a slinky or rope coil, ocean waves

33. LONGITUDINAL or Compressional Waves Vibrating particles move back and forth along the direction of the wave velocity Parts consist of compressions and rarefactions Ex. Sound waves

34. Sound Waves are Compression Waves Sound is produced when a compression is made. It requires a source to produce the compression and a medium for it to travel through. The more elastic the object, the faster sound travels. (The denser the medium, the faster mechanical waves can move)

35. 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.

36. 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 Resonance is the vibration of another object struck by a wave of the correct frequency. Since the forks are identical, the second one receives the correct frequency to begin vibrating.

37. Forces and Motion Forces can create changes in motion (acceleration)

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

39. Velocity Graphs ____________ Velocity (v) is the slope (rise over run) of a position (d) vs. time (t) graph

40. 40 The diagram represents the total travel of a teacher on a Saturday. Which part of the trip is made at the greatest average speed? F Q G R H S J T How do we work this one? Calculate v = d/t for each segment.

41. Acceleration Graphs Acceleration (a) is the slope of a velocity (v) vs. time (t) graph

42. 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 = v final – v initial time Units for acceleration m/s/s or m/s 2

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.

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. Use the ruler on the side of the chart and the equation for velocity. The answer was H. Measure from the center of ball 1 to the center of ball 2 and multiply by 4.

47. Unbalanced Forces Are forces that result in an object’s speed or direction being changed. +

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.

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

51. Newton’s 1st Law of Motion And an object at rest stays at rest

52. Newton’s 1st Law of Motion Unless there is an UNBALANCED force acting on it

53. Inertia or Newtons 1 st Law Tendency for an object to stay at rest or moving in a straight line at a constant speed. The mass (measured in kg) of an object determines its inertia

54. Newton’s 2nd Law of Motion Force = mass times 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/s 2

55. Newton’s 2nd Law of Motion If you apply a force to objects, the object with the least mass will have the greatest acceleration.

56. Newton’s 2nd Law of Motion The greater the mass 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 11 The frog leaps from its resting position at the lake’s bank onto a lily pad. If the frog has a mass of 0.5 kg and the acceleration of the leap is 3 m/s 2, what is the force the frog exerts on the lake’s bank when leaping? Formula chart says F=ma, m is mass in kg, a is acceleration in m/s 2. So,.5 kg x 3 m/s 2 = 1.5 N WRONG!

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

59. Newton’s 3 rd 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 Formula Page says that Momentum = Mass x Velocity So 15 kg. m/s = M x 30 m/s solving for M it is:

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 Use the formula Work = Force x distance Force of 20 N x 15 meters = 300 Joules Answer:

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

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 = force out / force in A machine can make this happen by moving the input force through a farther distance than the output force

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

66. Work Output = Resistance Force x Resistance Distance Work out = 18J = 6N x 3m Work Input = 30J done by the motor The difference is lost as heat due to friction, which is 30J – 18J = 12J Answer G

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 % Energy is lost due to friction between moving parts

68. Machines use power Power: the rate at which energy is used (work is done) Power = 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 45 If a force of 100 newtons was exerted on an object and no work was done, the object must have — Work = Force x Distance Work = 0 Force = 100 N so 0 J = 100 N x d distance must be 0 It did not move!

70. 6 Types of simple machines Some Simple Machines: Inclined plane Lever Pulley Screw Wedge Wheel and axle

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: 1) the masses of the objects, and 2) the distance from the center of one object to the center of the other

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 gravity (g) WEIGHT IS THE FORCE OF YOUR MASS PUSHING ON THE EARTH Unit of mass = kg Unit of acceleration = m/s/s Unit of weight = Newton

75. USE THE FORMULA PAGE Some of the problems require you to grid in an answer. Make sure you pay attention to the decimal point in the square in the middle.. 000000 111111 222222 333333 444444 555555 666666 777777 888888 999999