TAKS Objective 5

1. TAKS Objective 5 Motion , Forces and Energy

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

3. Kinetic Energy KE = ½ mv2 Ex: A moving car has the ability to do work on the light pole if it hits it.

4. Potential Energy2 possibilities Gravitational PE -Object lifted to some height Elastic PE - A stretched or compressed object (spring or rubber band)

5. Gravitational Potential Energy or Will 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/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 m = 95 kg g = 9.8 m/s2 h = 100 m 95 kg x 9.8 m/s2 x 100 = 93,100 joules C

7. 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.

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 heat energy is given off than is used to start it is exothermic An endothermicreaction absorbs heat energy and causes cooling

10. 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.

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.

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

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 V = I R so, 9V = I x 2 ohms or 4.5 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 Three forms of heating: • 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. . .

17. 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 108 meters/second 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 Solids do radiate heat to their surroundings

19. 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.

20. 50 A solar heater uses energy from the sun to heat water. The heater’s panel is painted black to — Convection is movement of heat in fluid matter, heat loss would be from a solid exterior – Not G 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 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 Emission is giving off – we want to absorb: Not F

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/s in space • ROYGBIV • Visible light is just one type of EM energy

24. Electromagnetic Spectrum All of the forms of radiation given off by vibrating electric charges 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

25. 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: deadly radioactivity

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

27. Waves - 2 Types

28. 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

29. 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

30. And the answer is? J 3300 Hz 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!!! Velocity = f λ OR 330 m/s = f x 0.10 m

31. 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

32. 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

33. 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)

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 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.

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

37. 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

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

39. 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.

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

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

43. Balanced Force • A force that produces no change in an object’s motion because it is balanced by an equal, opposite force.

44. 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

45. 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.

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

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

48. Friction Friction causes an object to slow down and stop. Since the amount of energy stays constant, the energy becomes heat.

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

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