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: • Kinetic (Energy of Motion) and • Potential (Stored Energy)

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. 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

5. 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

6. 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).

7. 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)

8. 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.

9. 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.

10. 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

11. 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. . .

12. 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 3.0 x 108 meters through empty space

13. 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

14. 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.

15. 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

16. Waves - Energy carried by rhythmic disturbances • Two types: • 1. E.M. radiation move through empty space • 2. Mechanical require a medium (air, water or any type of matter) for movement

17. Waves - 2 Types

18. 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

19. Velocity of all waves - v=f λ f-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

20. 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

21. 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.

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

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

24. 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.

25. 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

26. 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

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

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

29. 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

30. 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 divide by .25.

31. Are forces that results in an object’s motion being changed. Unbalanced Forces +

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

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

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

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

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

37. Inertia or Newtons 1st Law • 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

38. 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

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

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

41. 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/s2, what is the force the frog exerts on the lake’s bank when leaping? • A 0.2 N • B 0.8 N • C 1.5 N • D 6.0 N Formula chart says F=ma, m is mass in kg, a is acceleration in m/s2. So, .5 kg x 3 m/s2= 1.5 N

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

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

44. 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:

45. 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

46. 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:

47. 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

48. 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

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

50. 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 = WoutX 100% Win