Physics These are answers to the T-F and multiple choice questions on the practice final. Answers to all of the questions are available at the online PCA website (Moodle). 2nd Semester Final Review Qs 1 & 2 1. A transverse wave is transporting energy from east to west. The particles of the medium will move A east to west only B both eastward and westward C north to south only D both northward and southward Answer: D The particles would be moving back and forth in a direction perpendicular to energy transport. (By definition of a transverse wave.) The waves are moving westward, so the particles move northward and southward. 2. A wave is transporting energy from left to right. The particles of the medium are moving back and forth in a leftward and rightward direction. This type of wave is known as a A-mechanical B-electromagnetic C-transverse D-longitudinal Answer: D The particles are moving in the same direction that the wave is moving. This must be a longitudinal wave. A mechanical wave is usually longitudinal, but not always. Qs 3 & 4 3. Describe how the fans in a stadium must move in order to produce a longitudinal stadium wave. Answer: The fans will need to sway side to side. Thus, as the wave travels around the stadium they would be moving parallel to its direction of motion. If they rise up and sit down, then they would be creating a transverse wave. 4. A sound wave is a mechanical wave; not an electromagnetic wave. This means that a)A - particles of the medium move perpendicular to the direction of energy transport. b)B - a sound wave transports its energy best through a vacuum. c)C - particles of the medium regularly and repeatedly oscillate about their rest position. d)D - a medium is required in order for sound waves to transport energy. Answer: C or D The particles are moving in the same direction that the wave is moving. This must be a longitudinal wave. A mechanical wave is usually longitudinal, but not always. C true for all waves. Qs 5 & 6 5.A science fiction film depicts inhabitants of one spaceship (in outer space) hearing the sound of a nearby spaceship as it zooms past at high speeds. Critique the physics of this film. Answer: This is an example of phaulty physics in philm. Sound is a mechanical wave and so could never be transmitted through the vacuum of outer space, otherwise they would be creating a transverse wave. 6. Which of the following is not a characteristic of mechanical waves? a)They consist of disturbances or oscillations of a medium. b)They transport energy. c)They travel in a direction which is at right angles to the direction of the particles of the medium. d)They are created by a vibrating source. Answer: C The characteristic described in statement C is a property of all transverse waves, but not of mechanical waves. A mechanical wave is almost always longitudinal. Qs 7 & 8 7.The sonar device on a fishing boat uses underwater sound to locate fish. Would you expect sonar to be a longitudinal or a transverse wave? Answer: Longitudinal Only longitudinal waves are capable of traveling through fluids such as water. When a transverse wave tries to propagate through water, the particles of the medium slip past each other and so prevent the movement of the energy as a wave. 8. A wave has an amplitude of 2 cm and a frequency of 12 Hz, and the distance from a crest to the nearest trough is measured to be 5 cm. Determine the period of such a wave. Answer: Here is an example of a problem with a lot of extraneous information. The period is simply the reciprocal of the frequency. In this case, the period is 1/(12 Hz) which is seconds. Qs 9 & 10 9.A fly flaps its wings back and forth 150 times each second. The period of a wing flap is A 150 sec B 2.5 sec C sec D sec Answer: D The quantity 150 times/second is the frequency. The period is the reciprocal of the frequency. Using T = 1/f T=1/(150 Hz) = s 10. A kid on a playground swing makes a complete to-and-fro swing each 2 seconds. The frequency of the swing is _________. A 0.5 Hz B 1 Hz C 2 Hz Answer: A Frequency refers to the number of occurrences of a periodic event per time and is measured in cycles/second. In this case, there is 1 cycle per 2 seconds. So the frequency is 1 cycle/2 s = 0.5 Hz. Qs 11 & The period of a 440Hz sound wave is ____. Answer: sec. = sec. The quantity 440 times/second is the frequency. The period is the reciprocal of the frequency. Using T = 1/f T=1/(440 Hz) = s 12. If an echo is heard one second after the holler and reflects off canyon walls which are a distance of 170 meters away, then what is the speed of the wave? Answer: v-sound = d/t v = (2*170 m)/(1 sec.) = 340 m/sec. Q A teacher attaches a slinky to the wall and begins introducing pulses with different amplitude. Which of the two pulses (A or B) below will reach the wall first? Justify your answer. Answer: They reach the wall at the same time. Don't be fooled! The amplitude of a wave does not affect the speed at which the wave travels. Both Wave A and Wave B travel at the same speed. The speed of a wave is only altered when it moves from one medium to another. Q The teacher then begins introducing pulses with a different wavelength. Now which of the two pulses (C or D) will reach the wall first? Justify your answer. Answer: They reach the wall at the same time. Again, don't be fooled! The wavelength of a wave does not affect the speed at which the wave travels. Both Wave C and Wave D travel at the same speed. The speed of a wave is only altered when it moves from one medium to another. Q Two waves are traveling through the same container of nitrogen gas. Wave A has a wavelength of 1.5 m. Wave B has a wavelength of 4.5 m. The speed of wave B must be ________ the speed of wave A. a)one-ninth b)one-third c)the same as d)three times larger than Answer: C The medium is the same for both of these waves ("the same container of nitrogen gas"). Thus, the speed of the wave will be the same. Alterations in a property of a wave (such as wavelength) will not affect the speed of the wave. Two different waves travel with the same speed when present in the same medium. (Third time is a charm?) Qs 16 & A Doubling the frequency of a wave source doubles the speed of the waves. True False Answer: FALSE! The speed of a wave is unaffected by changes in the frequency. This is now the 4th time weve been beating that drum. 17. The speed of a wave depends upon (i.e., is causally effected by)... [List all that are true below.] a)the properties of the medium through which the wave travels b)the wavelength of the wave. c)the frequency of the wave. d)both the wavelength and the frequency of the wave. Answer: A 5th time? Qs 18 & The diagram below shows a transverse pulse moving to the right in a string. Which diagram best represents the motion of point P as the pulse passes point P ? A B C D Answer: A 20. The diagram below shows two waves traveling in the same medium for the same length of time. the two waves have different________? A. amplitudes B. frequencies C. speeds D. wavelengths Answer: A Q Notice that each consecutive harmonic is characterized by having one additional node and antinode compared to the previous one. The table below summarizes the features of the standing wave patterns for the first several harmonics. Just count the peaks and valleys. Harmonic# of Nodes# of AntinodesPattern 1st21 2nd32 3rd43 4th54 5th65 6th76 Q The diagram below shows straight wave fronts passing through an opening in a barrier. The wave phenomenon is called A. Reflection B. Refraction C. Polarization D. Diffraction Answer: D Q The diagram below shows straight wave fronts bending as they pass from one medium into another. The wave phenomenon is called A. Reflection B. Refraction C. Polarization D. Diffraction Answer: B Q The water waves below are traveling along the surface at a speed of 2 m/s and splashing periodically against Wilbert's perch. Each adjacent crest is 4 meters apart and splashes Wilbert's feet upon reaching his perch. How much time passes between each successive drenching? Explain your answer. Answer: If the wave travels 2 meters in one second then it will travel 4 meters in 2 seconds. If Wilbert gets drenched every time the wave has traveled 4 meters, then he will get drenched every 2 seconds. f = T = 2 sec. Q When an opera singer hits a high-pitch note, a glass on the opposite side of the opera hall shatters. Which statement best explains this phenomenon? A. The frequency of the note and resonance frequency of the glass are equal. B. The vibrations of the note are polarized by the shape of the opera hall. C. The amplitude of the note increases before it reaches the glass. D. The singer and glass are separated by an integral number of wavelengths E. Mr. Bruce has been playing around with the Van de Graph generator again. Answer: A This is referred to as sympathetic vibrations. Q The diagram at the right shows a ray of light, R, entering glass from the air. Which path is the ray most likely to follow in the glass? Answer: C It is bent towards the perpendicular (normal) in going into a more dense medium (glass). Q The diagram below shows sunglasses being used to eliminate glare. Which wave phenomenon of light is represented in the diagram A. dispersion B. diffraction C. internal reflection D. polarization Answer: D Polarizing sunglasses allow waves to vibrate in only one plane. (perpendicular) Q The diagram below represents straight wave fronts approaching an opening in a barrier. Which of the following best represents how the wave will appear after passing through the opening? A B C D Answer: D (This is referred to as diffraction.) Q T F 28. There is more pressure at the bottom of a bathtub 50 cm deep than at the bottom of a pitcher of water 100 cm deep because of the greater volume of water. T F 29. An object floating displaces water less than its own weight. T F 30.An object sinking experiences a buoyant force, though it is less than its weight. T F 31.In a series circuit, the current is the same through all series components. Q T F 32. Density ( ) is the ratio of mass to volume. T F 33. Liquids cannot be compressed into smaller volumes. T F 34. If the end of a rope is tightly tied to a post and a wave is generated, when it reaches the end the reflected wave will change its phase 180 o. T F 35. Standing waves are actually moving, interfering waves, though they appear to be stationary. T F 36. If you twist two Polaroid lenses such that one polarizes light in a plane perpendicular to the other no light gets through. Q T F 37. A decibel is an exponent 1/10th of a Bel. T F dB is 100 times as loud as 40 dB. T F 39. The speed of sound in air is about 340 m/sec. (Memorize the speed of sound in air.) T F 40. The Tacoma Narrows Bridge did not collapse in 1940 due to the extreme intensity of the winds, but due to resonance which was set up. T F 41. A pendulum bob is released 20 o from its equilibrium position. Will the motion be simple harmonic? (Honors physics only) (20 dB difference = 10 2 ) It seems like its 4x to our ears. Q T F cubic meter of water has a mass of 10 3 kg. (HONORS only) T F 43. A metal weight has a higher heat capacity than glass since it gets hotter more quickly. T F 44. Conduction requires actual contact between the substances. T F 45. Air is a good insulator. (Also 1 gm/1 cm 3 and 1kg/1 liter) Q T F 46. If a person is traveling on a train and shines a flashlight from it, someone looking at it on the ground will say that the light is traveling faster than cthe speed of light. T F 47. When traveling at relativistic speeds the traveler is well aware of how time is slowing down for him when he looks at his watch, as it is running slower. T F 48. In a series circuit, there is only one path for the current. T F dB is the threshold of hearing, meaning that the average person cannot hear a sound with an intensity lower than that. Q 50 and 51 T F dB is the minimum sound loudness difference that the average person can discern. T F dB is 10 3 (1000) times louder than 40 dB. Q 52 & 53 52) Archimedes discovered his principle about buoyancy while A) swimming. B) studying about Pascals principle. C) talking with Bernoulli. D) teaching at MIT. E) taking a bath. 53) Diffraction is A) the bending of a wave as it travels from one medium to another. B) the bending of a wave around a corner. C) complete constructive interference. D) the effect which causes the dual wave-particle properties of matter Q 54 & 55 54) Refraction is A) the bending of a wave as it travels from one medium to another. B) the bending of a wave around a corner. C) complete constructive interference. D) the effect which causes the dual wave-particle properties of matter. 55) ____ of a wave will produce resonance of a sound wave in a tube over water. (As in the lab) A) of a wavelength B) of a wavelength C) 1 full wavelength D) 2 full wavelengths Q 56 & 57 56) ____ of a wave will produce resonance of a sound wave in a tube with both ends open. A) of a wavelength B) of a wavelength C) 1 full wavelength D) 2 full wavelengths 57) In the picture shown, the ship is using ___ to detect underwater obstacles. A) holograms B) stereograms C) refraction D) sonar Qs 58 & 59 58) Consider the decibel chart supplied. How many times louder is a vacuum cleaner than a mosquito buzzing? _____ times as loud (40 dB 70 dB) A)3 B) 10 C) 30 D) ) Compared to the person on the left, the Doppler Effect tells us that the person on the right will hear ________ pitch sound. A) a higher B) a lower C) an oscillating D) the same Qs 61 & 60 61) What happens to the period (T) of a simple pendulum when the length is made four times longer T = 2 A) The period is cut in fourth. B) The period doubles. C) The period increases by a factor of. D) The period increases by a factor of 4. 60) As a weather balloon moves higher in the atmosphere A) it gains weight. B) it loses volume. C) it expands. D) None of the above Qs 62 & 63 62) Which of the following equations regarding pressure is correct? A) P = A(density times area) B) F = P/A(force is pressure per unit area) C) P = F/A (force per unit area) D) P = mass/Vol. (pressure is mass per unit area density) E. None of the above. 63) Which is denser, ice at 0 o C or water at 4 o C? (Think: ice floats in water.) A) Ice at 0 o C B) Water at 4 o C) Same substance, so they have the same density. D) It depends on the phase of the moon Q 64 (Change) 58) When jumping a car battery with cables, the last cable (negative one) should be connected to A) the terminal of the running car. B) the terminal of the car being jumped. C) the + terminal of the car being jumped. D) the metal frame of the car being jumped. E) the + terminal of the running car. Qs 65 68 Identify the following waves: 65) ___ Standing wave (Not C) 66) ___ Longitudinal wave 67) ___ Transverse wave 68) ___ electromagnetic wave Q 69 69) What was the purpose of the Michelson-Morley experiment? A) To prove Einstein right. B) To show that light always travels at 3.00 x 10 8 m/s. C) To show that light will travel at a slightly greater speed (about 0.01% faster) East-West as compared to North-South. D) To show that the nucleus is a dense center in an atom. E) To determine the velocity of sound in a vacuum. Although they ended up discovering evidence which later showed Einstein to be correct, their goal was to demonstrate that light travels faster in a E-W direction than in N-S due to the rotation of the earth. That was how waves behaved. Einstein had not yet stated his special theory of relativity. Q 70 70) How did Einstein refer to space and time in his special theory of relativity? A) As a quark. B) As a gravity wave. C) As space-time continuum. D) As the uncertainty principle. E) He distinguished between the 3 dimensions of space as well as time and did not combine them in any way. The concept of space and time being inexorably interconnected was a revolutionary concept, and the essence of relativity theory. Q 71 71) When did Einstein publish his Special Relativity theory? A) 1881 B) 1887 C) 1900D) 1905 E) 1916F) 1919 G) 1921H) B) How about his General Relativity theory? 67C) When did a British astronomer verify his General Theory of Relativity? 67D) When did Einstein receive his Nobel prize? You need to memorize the dates for special and general relativity (1905, 1916) as well as the date that Einstein received the Nobel prize (1921) and Eddington verified his general theory through an eclipse (1919). Q 72 72) Einstein received the Nobel prize for A) the special theory of relativity. B) the general theory of relativity. C) explaining the photoelectric effect. D) Explaining Brownian motion. Although it was given for his accumulated efforts in the field of physics it was specifically given for explaining the photoelectric effect! Q 73 & 75 (74-dup of 72) 73) The thicker the wire through which current flows A) the less resistance to current flow. B) the greater resistance to current flow. C) will not affect current flow at all. D) the less the potential difference. Thinner wire causes greater resistance as does a longer wire, just as a narrower river provides greater resistance to water flow. 75) When did the British astronomer Arthur Eddington verify Einsteins general relativity theory during an eclipse of the sun? A) 1881B) 1887 C) 1900D) 1905 E) 1916AB) 1919 AC) 1921AD) Sp. Th., 1916-Gen. Th., 1921-Nobel prize Q 76 & 77 76) 70 dB sounds like ___ times as loud as 40dB to the human ear. A) 30 B) 3 C) 2 3 = 8 D) 10 3 = 1000 Though in reality it is 10 3 (1000 x) louder, to our ear it sounds 2 3 or 8 times louder. 77) A transformer which changes an AC voltage from 120VAC to 12,000VAC is referred to as a _________ transformer. A) High voltage B) interlocking C) step up D) step down If it increases the voltage it is step-up; decreasing means to step down. Q 78 & 79 78) What is the charge of the following point charge? The electric field lines should help you. A) positive B) negative C) either positive or negative D) Cannot be definitively determined from this drawing. Remember to use a + test charge. 79) What is the charge of the following point charges, from left to right? The electric field lines should help you: A) positive-negative B) negative-positive C) negative-negative D) positive-positive Q 80 & 81 80) What can we say about the electric field inside the circular conductor shown on the right side of the pic below? A) It is pointing up out of the picture B) It is pointing toward the right (away from the positively charged plate) C) It is pointing toward the left (toward the negatively charged plate) D) The field is zero inside an enclosed conductor. 81) What can we say about the electric field on the plates shown in the picture below? A) L:positive R:negative B) L:negative R:positive C) L:negative R:negative D) L:positive R:positive Remember to use that + test charge. Q 82 & Q83 82) The globes below (not touched) have been A) charged by conduction B) charged by induction C) charged by induction through grounding As you can see, no grounding path was provided, and since it was never touched by the charged rod induction. 83) The globe below and to right (touched) has been A) charged by conduction B) charged by induction C) charged by induction through grounding Q 84 & Q85 84) The globe below (not touched) has been A) charged by conduction B) charged by induction C) charged by induction through grounding As you can see, a grounding path was provided, and since it was never touched by the charged rod induction through grounding. 85) Where should the cable from the negative terminal of the automobile which has a charged battery be connected on the automobile with a dead battery. A) B) C) D) If A and the battery has a leak, it could easily explode. Q A)transformer B) diode bridge C) RC smoothing circuitry D) 1 diode 86) What is the component for step 1 above? 87) What is the component for step 2 above? 88) What is the component for step 3 above? Q A) smooth our ripples of the DC current B) convert DC to AC C) convert AC to DC D) lower the voltage 89) What does the step 1 portion of circuitry do? 90) What does the step 2 portion of circuitry do? 91) What does the step 3 portion of circuitry do?