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Solve Prob. 1796 if the cord and force P = 50 N are

Engineering Mechanics: Statics & Dynamics | 14th Edition | ISBN: 9780133951929 | Authors: Russell C. Hibbeler ISBN: 9780133951929 123

Solution for problem 17-97 Chapter 17

Engineering Mechanics: Statics & Dynamics | 14th Edition

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Engineering Mechanics: Statics & Dynamics | 14th Edition | ISBN: 9780133951929 | Authors: Russell C. Hibbeler

Engineering Mechanics: Statics & Dynamics | 14th Edition

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Problem 17-97

Solve Prob. 1796 if the cord and force P = 50 N are directed vertically upwards

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CHAPTER 1: WHAT IS COGNITIVE PSY/RESEARCH METHODS OVERVIEW According to rationalists, how is knowledge obtained According to empiricists, how is knowledge obtained ­ Innate ­ External ­ Acquire knowledge through reason ­ Knowledge comes from experience ­ Introspective and logical analysis ­ Knowledge is learned and acquired ­ Reality is in the physical world Cognition is defined as the study of processes by which sensory inputs is transformed, reduced, elaborated, stored, recovered, and used. Be able to recognize descriptions or examples of how these functions differ. Transform Information Transformation Information ● External information must be transformed into an internal code that is processed by our brain ○ Electrical, mechanical, and chemical stimulation of our receptors is transformed into perceptual experience ● Ex. ○ Mental transformation ○ You will see two pair of circles. As quickly as you can, decide which circle is biggest ○ Reduce Information ● Cognitive processes tend to reduce our experiences ● Memories of events are not perfect recordings Ex. Which is the real penny Elaborate Information ● Recollections tend not to be perfect duplications of what was originally learned ● Recollections are more like reconstructions that elaborate on a theme ● Students heard list of random words that could be one of 4 categories and would later recall other words from those categories that had not been listed 1 Store and Recover Information ● Memory​ involves mental operations that store information as well as recover or retrieve it at the appropriate times ● Why does memory sometimes fail ● “How is it that our memory is good enough to retain the last triviality that happens to us, and yet not good enough to recollect how often we have it to the same person” (La Rochefoucauld) Use Information ● Remembering that an exam is coming up (​prospective memory)​ ● Comprehending what people say to us (​language understanding​) ● Answering, “Do they grow coffee in Paraguay” (​reasoning) How do the behaviorist and cognitive psychology approaches differ What are their views on mental processes Behaviorists Cognitive Psychologists Approaches ● Watson, Skinner ● Wanted to know “what’s in ● Operant conditioning the black box” ○ Consequences of behavior determined if behaviors change in frequency or intensity ○ If pushing a button = food, pushing a button will increase in frequency Views on Mental ● To understand humans, scientists must look Processes exclusively at behavior (i.e. the observable) rather than hypothesizing about mental processes ● Stimulus ­ Response (S­R) approach to the analysis of behavior ● Stimulus → organism → ● Stimulus→ blackbox→ response response ● Bell → don’t care → saliva ○ Used behavior to infer mental states and cognitive processes What four disciplines gave rise to modern cognitive psychology Gestalt Psychology Human Factors Research Computer Simulation Cognitive Neuroscience ● The scientific study of the relationship between brain structures, neurological activity, and cognitive function (ex. Broca in the 1860s) How did Gestalt psychology contribute to the development of cognitive psychology Gestalt Psychology ● Gestalt (German for “form”) ­ experiencing the whole form or pattern rather than the individual components ● Gestalt psychology seeks to discover the principles that determine how people’s perception of the whole is derived from their perception of individual parts 2 What is the purpose of human factors research ● WWII military concerned w/ people doing their jobs ● Concerned with helping people to​ perform tasks efficiently and safely ● Focuses on the limits of our mental capacities (when they didn’t see an enemy on a radar) and how they constrain our actions How did interest in computer simulation contribute to the development of cognitive psychology ● Approach has been used to create models of thinking ○ Some terms derived from the computer metaphor: memory capacity, storage, retrieval, encoding, and decoding ● Goal of computer simulation is to have a computer respond to a problem by producing an output that matches the behavior of a real person confronted with the same problem ● 2 major types of models ○ SERIAL PROCESSORS ○ PARALLEL DISTRIBUTED PROCESSING, NEURAL NETWORKS Explain the difference between serial processing and parallel distributed processing in computer models of human information processing. ● SERIAL PROCESSORS ○ Sequential processing of information (steps) ○ Input → step 1 → step 2 → step 3 → response ○ Way we understand human memory and problem­solving ● PARALLEL DISTRIBUTED PROCESSING, NEURAL NETWORKS ○ Different processes at once ○ Information processing is a series of decisions and actions produced at the same time ○ Input → process 1, 2, & 3 → response ○ Way we understand pattern recognition Explain how response accuracy, produced response, and response latency differ as measures of cognitive processes. Why would a researcher use each method Response Accuracy Produced Response Response Latency Definition ­ Measures whether or not a ­ The actual responses ­ (Response time or reaction to participant makes a correct participants make when they time) measures the amount of response in a specified period of freely recall an event time a participant takes to make time (memory) a response ­ Assumed to be filled with cognitive processes 3 Why Gives researchers an idea of researchers use how a participant interprets a method story or what details they attend to Example Facial recognition tasks → A week after reading stories Response latency for accuracy is worse when faces are about the first day of school first­graders as they performed inverted reflective of either Mexican or mental arithmetic. Took less Vigilance task ­ must detect subtle U.S. culture, participants time to add 1 + 5 than to add 3 change in movement of clock’s mistakenly recalled events + 5 and the same amount of hand → accuracy was not affected from other cultures in ways time to add 1 + 6 by having a hangover from binge there were consistent with their drinking own culture What do cognitive psychologists assume about response latency ● Cognitive Latency​ (response time or reaction time) measures the amount of time a participant takes to make a response ○ Time between the moment a stimulus is presented to the moment a response is made by the participant ○ Assumed to be filled with specific cognitive processes ○ Longer = more cognitive processes = harder ○ Ex. Response latency for first­graders as they performed mental arithmetic. Took less time to add 1 + 5 than to add 3 + 5 and the same amount of time to add 1 + 6 4 CHAPTER 2: THE BRAIN AND COGNITION Name and describe the 3 major parts of a neuron. ● Dendrites​ ­ branch­like fibers that conduct input from other neurons into the cell body ● Cell body​ (soma)­ contains cell nucleus; processes input and initiates transmission of information if input is strong enough ● Axon​ ­ a long fiber extending from the cell body which conducts electrical activity to other neurons (via synapses onto their dendrites) How is information transmitted through a neuron ➢ Dendrite, cell body, axon ➢ Comes from other neurons through synapse → Input to the dendrite → cell body → output in axon ➢ Comes in from other neurons through synapse → dendrites How do neurons communicate with other neurons What are the roles of the synapse and neurotransmitters ● Synapse​ ­ the gap between neurons ○ When an electrical signal is transmitted down the axon, the synapse fills with packets of chemicals called neurotransmitters ● Neurotransmitters​ ­ allow an electrical impulse to occur or prevent an electrical signal ○ After acting on post­synaptic neuron, NTs are broken down or taken back up into axon ○ Deficits in neurotransmitters can lead to cognitive difficulties ○ Ex. Neurotransmitters dopamine​ produced in thesubstantia nigra​ stimulates neurons that control muscles ○ People with Parkinson’s disease have lost at least 80% of the neurons in the substantia nigra and thus their motor system neurons cannot control movement What are the 3 major divisions of the brain What are the functions of each Name Hindbrain Midbrain Forebrain Function ­ Controls automatic processes ­ Relay center for sensory ­ Surrounds the midbrain that regulate life­support information entering the brain functions ­ Includes amygdala (fear) and ­ Contains fibers critical for hippocampus (memory) ­ Includes thecerebellum voluntary movement → Involved in balance ­ Includes thecerebral cortex andcoordination of ­ Includes thesubstantia nigra (wrinkled outer portion which is voluntary movement → Produces NT dopamine mostly cell bodies and dendrites of → Plays a role in (Deteriorated in Parkinson’s neurons) high­level cognitive tasks patients) 5 Be able to locate the cerebellum. Which brain division includes the cerebellum LOCATED IN THE ​ HINDBRAIN Which brain division includes the substantia nigra Why is the substantia nigra important What degenerative disorder is associated with this structure ● Midbrain contains the​ubstantia nigra ● Substantia nigra produces the neurotransmitt​opamine ● Parkinson’s​ is associated with deterioration of this structure What is the cerebral cortex Why is it folded What are sulci and gyri ● Forebrain includes thcerebral cortex ● The cerebral cortex is the wrinkled outer portion (mostly cell bodies and dendrites of neurons) ○ The folds allow for a lot more cell bodies to be present → more complex thought (ex. mouse brain is pretty smooth) ○ Regulates mental processes enabling complex learning, thought, ­Sulci orfissure are the valleys (singular: sulcus/fissure) and language ○ Folds allow more cortex (increased surface area) to fit in skull ­Gyri​ are the hills (singular = gyrus) Describe the corpus callosum and its function. ● Corpus callosum​ : largest commissure connecting left and right hemispheres ○ Function to connect the two hemispheres and have them communicate ■ When cut (or not developed fully), people experiensplit brain ■ Split brain = one hemisphere has little knowledge of signals processed by other hemisphere 6 Explain what is meant by lateralization and localization. Lateralization Localization Brain is divided into two halves Specific brain areascontrol specific parts of the body Two of every structure from forebrain to hindbrain Localization of function​ is the hypothesis that different functions of thought are performed in different locations in Halves of cortex are callehemispheres the brain Each hemisphere is dominant for particular functions What is phrenology In what way was it correct In what way was it incorrect ● 1835: Gall proposed that different mental abilities were localized in different areas ○ Phrenology​ ­ assumed the size of areas was in proportion to the amount of a person’s ability and could be analyzed by measuring skull bumps ■ Phrenology has been DEBUNKED, but other aspects of the localization hypothesis still hold true (i.e. thought is not related to skull bumps BUT mental functions are localized to specific areas) Be able to identify the locations and describe general functions of the four lobes of the cerebral cortex. Frontal Lobes ● Higher cognitive functions including attention, problem solving, communication Parietal Lobes ● Provide ability to locate objects in space (including our body space and left/right) ● Allow spatially based mathematical thinking Temporal Lobes ● Processing of sound, language, and long­term memory Occipital Lobes ● Contains the primary visual areas of the cortex What is meant by “brain plasticity” ● “Plastic” refers to the brain’s ability to be modified by experience ○ Brain is able to be plastic because new connections form between neurons throughout life (and experience then refines these connections) ■ Ex. Occipital lobe (visual area) active when visually impaired people who have been blind since birth read Braille What does EEG measure What sort of equipment is used What is a major strength of this technique ● Electrodes on the scalp record the electrical activity of underlying brain regions ● Uses electrode helmet vs magnet ● Good temporal resolution 7 What does PET measure What somewhat invasive procedure is required for this technique Provide a strength of PET. ● PET scans indirectly measure blood flow to regions of brain most active at a given time ● Radioactive glucose injecte into bloodstream ○ Glucose emits positrons ○ Brain is scanned to detect energy released from positrons ● Strength: better spatial resolution than EEG What does fMRI measure ● Uses a large magnet to infer brain activity ● Blood flow increases to active brain regions ● Amount of oxygen increases, which affects the blood’s magnetic properties and brain’s magnetic signal (BOLD signal = Blood Oxygen Level Dependent) What is the subtractive method Which two research techniques use this method ● Subject is scanned twice ○ During baseline : task requiring minimal cognitive processing ○ During task : requiring function of interest ● PET and fMRI use this method How do fMRI and rTMS differ in the way they use magnets fMRI ● Functional Magnetic Resonance Imaging ○ Amount of oxygen increases, which affects the blood’s magnetic properties and brain’s magnetic signal (BOLD signal = Blood Oxygen Level Dependent) rTMS ● Repetitive Transcranial Magnetic Stimulation ○ Magnetic pulses repeated over an area of the head can increase or decrease specific brain area activity (fairly new) 8 CHAPTER 3: ATTENTION Define attention, and name the three general properties of attention. Attention ● Set of cognitive processes that allow us to concentrate on one set of events in our environment ● Controls mental environment by choosing the events that enter our consciousness 3 Properties ● Limited ● Selective ● Universal Describe the Method Clock task. How does it show that attention is limited (LIMITED) Mackworth Clock Task ● Proved that attention diminishes with time ● Participants watched a red dot moving around a clock. When it skipped a position participants were told to press a button. ● Found that participants missed more targets the longer they performed the task Explain preattentive and focused attentional processing. (SELECTIVE) ● Preattentive Processing ○ The ability to focus on relevant event to the exclusion of all else ○ Can occur so quickly that perceiver is unaware of all the stimuli that have been excluded ○ Ex. Locate the red circle (notice the “pop out” effect) ● Focused Attentional Processing ○ Processes by which the attentional system deeply processes stimuli in the environment ○ Required when target shares features with other objects in a display ○ Ex. Locate the red circle (notice how features are assessed sequentially and with effort) 9 When are you likely to use each type ● If they don’t share features = preattentive processing ● If target shares features = focused attentional processing What are the orienting reflex and habituation (UNIVERSAL) ● Orientation Reflex ○ Basic biological reaction to turn our attention to any change in the environment ○ A universal component of human cognitive architecture ○ Helps us to identify the stimulus ● Habituation ○ Occurs when we do NOT orient to a stimulus because it is no longer novel and doesn’t capture our attention ○ Diminishing of a response because we are used to it How are each adaptive to survival ➢ Adaptive to survival because it protects us from unknown ➢ Habituation helps because then we don’t waste our resources on things that happen again and again Recognize functions and locations (i.e. lobe to where the sensory cortices project) of the where and what circuits. (UNIVERSAL) Where/What Circuits ● Where circuit ­ processes information about the spatial location of objects ○ From visual or auditory cortex → parietal lobe ● What circuit ­ allows memories to be activated in order to recognize the object ○ From visual or auditory cortex → temporal lobe ATTENTIONAL SPOTLIGHT Explain the attentional spotlight metaphor. Attentional spotlight ● A cognitive ability to focus in or sharpen our attention ● Metaphor: a spotlight on stage ○ Attention can be moved and refocused ○ It takes time to shift attention from one thing to another ○ Attention has a limited range Be able to recognize the results and conclusions of the Posner, Snyder, and Davidson (1980) study. (I would provide the authors and a brief description of the task in the question prompt.) ● Study ○ Eyes focused on the center of the screen ○ Arrow cue pointing to the right or left box on the screen (correct direction 80% of the time...20% misleading) ○ Target stimulus (some shape) will appear in either the left or right box ○ Observer must respond to the target immediately after detecting it ● Results ○ Decreased reaction times when the cue was valid (direction of arrow pointed to the correct stimulus box) ○ Slower reaction times for invalidly cued targets ● Conclusions ○ Can shift attentional spotlight without moving our eyes but it’s not instantaneous ○ That it takes time to shift the spotlight if the cue is invalid ■ If you’re already looking at the cue but it’s only 20% correct, you have to shift to the other spot 10 Explain how the flanker task can be used to measure the width (i.e. distance between boundaries) of the attentional spotlight. What is the width of the spotlight ● Target is the center letter in a string of 5 letters ○ If “H” or “K”, press right ○ If “S”, press left ● K K H K K ● S S H S S ***Flankers only have effect if they are within 1 degree of the central target*** 1 degree = width of 1 thumb nail outstretched What is subitizing What is the upper limit of subitizing Subitizing ● The ability to determine small numbers of items presented simultaneously ● Takes longer to name how many dots there are when there are more ● Research on subitizing has shown that attentional spotlight can hold up to four item ● We can estimate four or few items automatically ● More than four items have to be counted UPPER LIMIT = 4 11 PLATFORM FOR ATTENTION What is sensory storage ● A buffer memory system that hosts an incoming stream of information long enough for us to pay attention to it ● Separates incoming stimuli from everything else in cognitive system ● Allow sensory information to briefly remain after the stimulus ceases For any memory system we ask ● What is its capacity ● What is its duration ● How does forgetting occur ● How do we code the information Capacity of sensory storage Describe the partial report procedure designed by Sperling and explain how it can be used to measure capacity of visual sensory storage. Whole Report ● Arrays of 2 ­ 12 letters flashed for 50 msec (really fast) ● Participants had to recall all the letters ○ Could only recall 4.5 letters when stimulus contained more than 5 letters ○ Claimed they saw more than they could report (perhaps because the information left sensory storage faster than they could repeat it) Why was this method an improvement over the whole report technique (what was wrong with the whole report technique) ● Could only report 4 letters but said they could see more! ● This was a low measure of sensory capacity storage ● So then they developed the partial report How was the partial report procedure used to study duration of sensory storage and what were the findings Partial Report ● Participants were shown a display of items but asked to report only a selected part of the display corresponding to a sound pitch 1. Participants shown display 2. Sound goes off AFTER 3. Participants must recall the row of letters that corresponded to the sound ● IMPORTANT because it shows that our capacity of sensory memory is larger than we can report (fades away) ● If you can recall 75% of ANY row that means that technically we could report 75% of the whole thing and therefore we have a much larger capacity than the whole report suggests 12 What limitation in the whole report technique was the partial report technique use by Sperling (1960) designed to overcome Partial part designed to overcome our limited memory span. By cuing participants to identify a specific row it indicated that subjects DO have access to ALL of the letters in a visual buffer (we see them all) but that we have difficulty in reporting them before they fade away. Explain how the partial report procedure designed by Sperling (1960) can be used to measure capacity and duration of visual sensory storage. What is the approximate capacity and duration Capacity Partial report revealed that immediately after the stimulus offset, participants could recall most letters. When the auditory cue was delayed even 1 second, we lose sensory storage. Within a half second, ⅓ of the storage is gone. ● If you wait too long you can’t access the sensory storage What is the cocktail party phenomenon ● The ability to shift attention immediately when a word or voice from a peripheral stream of speech captures your attention (if you hear your name in a different conversation, if something is bright in our peripheral, if something is loud) Describe the dichotic listening task. What is the participant instructed to do ● Participants wear headphones that present a different message to each ear (“channel”) ● Is supposed to attend to one channel and ignore other ● Must repeat back (“shadow:) what is said in attended channel ● Participants are generally unaware of content of unattended channel ○ Can’t detect change of language ○ Can’t detect if senses are nonsensical ● Participants ARE aware of content on unattended channel if own name is spoken or if message contains sexually explicit words ATTENTION AS A FILTER How does attention filter sensory input Describe the role of early­ and late­selection attentional filters. ● Idea that we can’t attend to everything. Limited resource. ● Not everything can reach our brain ● Attention filters what comes in and what doesn’t ● WHERE does this attentional filter occur ● Perceptual processes = identifying objects 13 ● Early­selection filter ○ Attention is captured by the physical properties of a stimulus in the environment prior to perception ○ ● Late­selection theory ○ Unattended stimuli are perceived and are filtered ouonly if they are not relevant to the context ○ Some stimuli havepermanently low threshol (always relevant) and are unconsciously retained even if they are not related to current mental processes ■ Your name ■ Smell of gas ■ Someone yelling “Fire!” ○ How did the Corteen and Wood (1972) study involving dichotic listening and mild­electric shock provide evidence for late­selection of attention What did they measure ● Dichotic listening task with mild electric shock to certain words ● Participants showegalvanic skin response to shock­associated words presented in unattended channel ○ EVEN THOUGH they were in the unattended channel they were getting sweaty ○ Important because it suggests a LATE selection response ○ Galvanic skin response measures electric conductance of skin AUTOMATIC AND CONTROLLED PROCESSES What are the characteristics of automatic and controlled processing Automatic processes​ are the attentional processes not consciously controlled ● Evoked without making decisions or necessarily intending them to occur ● Require minimal attentional resources Controlled processes are the processes that are deliberately attended to ● Often available to conscious and understanding ● Exist on a continuum with automatic processes ● With extensive practice, a controlled process can become automatic ○ Closed skill ■ A task that can be reliably accomplished under a variety of predictable circumstances (ex. tying) ○ Open skill ■ A task that requires considerable conscious attention to perform in unpredictable circumstances (ex. driving in snow) Why is it beneficial to have both types ● Automatic processes require minimal attentional resources and allow for a quick response ● Controlled processes allow reflection and adjustment but are resource demanding 14 Describe the Stroop effect, and explain how it reveals a conflict between automatic and controlled processing. Stroop effect ● Participants must name the color of the ink ● Longer response times when there is conflict between ink and color name because we automatically readred, word (​ green,green ​lu, yellow) ● Automatic response = read word ● Incongruent example is shower because there’s a conflict ● Reveals that we have an automatic response but when it is incongruent it requires controlled processing ATTENTION AS A RESOURCE Explain the capacity theory of attention. ● Attention is a resource distributed among tasks ● The ability to focus varies with number and complexity of tasks and how mentally energized we are ● Performing a task costs resources ● If costs exceed our capacity, performance suffers Recognize the differences between descriptions/examples of attentional blink, repetition blindness, change blindness, and inattentional blindness. ● Attentional blink ○ The moment when a person is shifting attentional focus and is unable to attend to new target event ○ “The phenomenon that the second of two targets cannot be detected or identified when it appears close in time to the first ○ RAPID SERIAL VISUAL PRESENTATION METHOD Recognize a description of the rapid serial visual presentation method. Rapid serial visual presentation method ● Letters presented rapidly ● Must press button if either of two target letters are shown Why is it used → Used to study the attentional blink and repetition blindness → Shows that performance is worse when participants are looking for TWO targets especially if right after the other target → Repetition: K and then K again, you wouldn't’ press a button for the second K ● Repetition blindness ○ Decreases in the ability to perceive repeated stimuli during a rapid serial presentation of items ○ Ex. two consecutive letters are “B”, may remember seeing only B ■ Not due to inability to visually separate letters because occurs if letters are in different cases (i.e. B and b) or sizes ● Change blindness ○ Inability to notice when a change occurs in a visual stimulus ○ Ex. the video when the person asking directions is changed 15 ○ ● Inattentional blindness ○ Failure to notice stimuli when focus of attention is elsewhere ○ Ex. When performing two attention­demanding task (focusing on counting the # of passes people in white shirts are making...gorilla comes through...many people did not see it) ○ Ex. Using cell while driving NEUROPSYCHOLOGY OF ATTENTION In which cortical lobe would a patient with simultanagnosia or hemispheric neglect likely have a lesion Simultanagnosia​ ­ bilateral parietal lobe damage Hemispheric neglect​ ­ lesion to parietal lobe (usually right) What are the symptoms of each disorder Simultanagnosia ➢ Individual is unable to attend to more than one object at the same time ➢ Often bumps into objects Hemispheric neglect ➢ Individual is unable to attend to opposite visual field (usually left) In what ways are Parkinson’s disease and ADHD behaviorally similar ● In ADHD and advanced stages of Parkinson’s disease, symptoms include attentional problems What is the name of the neurotransmitter that is associated with both disorders → Dopamine 16 CHAPTER 4: PATTERN RECOGNITION ● Pattern recognition​ ­ is the use of fragmentary pieces of sensory information to create a higher­level identification of what has been experienced ● Allows us to evaluate sensory information in a structured, predictable way What are the roles of bottom­up processing and top­down processing in pattern recognition ● Bottom­up processing ○ Extracting primitive or basic elements from a stimulus and creating a higher representation of it ○ The physical element ● Top­down processing ○ Occurs ​afte a preliminary guess is made about a stimulus through bottom­up processing ○ Using knowledge stored in long­term memory (exceptions, context, biases) to select features of the object for further analysis to complete identification GESTALT PERCEPTION ­ The idea that we perceive the form or configuration of things before we understand their parts Be able to explain and recognize the name of the principle underlying Gestalt perception. The principle of Pragnanz ● The perception of a stimulus will be organized into “as cohesive a figure as possible” ● Cohesive figure = a “good” figure = symmetrical, simple, closed, and regular ● See (A) as composition of figures in (C) rather than the actual lines that do compos it Be able to explain and give (or recognize) examples of the laws of proximity, similarity, closure, common fate, symmetry, and good continuation. ● Gestalt psychologists used the principle of Pragnanz to define 6 basic laws of automatic perceptual grouping 1. Law of Proximity ­ Elements that are closer together will be perceived as a coherent group and be differentiated from items that are far from them ­ 2. Law of Similarity ­ Elements that look similar will be perceived as part of the same group ­ Similarity can be based on size, color, brightness, shape, or orientation ­ (red circles, black circles) ­ Stimuli for test of color vision utilize law of similarity ­ Ex. People with red­green color blindness see “12” but not “5” ­ 17 3. Law of Closure ­ The experience of seeing a figure as a closed unit, even when the observer knows there are open spaces ­ Gives rise to ​illusory contours ­ Visual illusions that evoke the perception of an ​ edge​ without a luminance or color change across that edge ­ Ex. Kaniza triangle (1976) ­ ­ Ex. People perceiving one large circle (rather than a set of 10) ­ 4. Law of Common Fate ­ If two or more objects are moving in the same direction at the same speed, they will tend to be perceived as a group that shares the same destiny ­ 5. Law of Symmetry ­ 1. Images that are perceived as symmetrical are experienced as belonging together ­ 2. People tend to find symmetry in a figure even if it is otherwise disordered ­ ­ Preference for symmetry is evident early in development: 3 month old infants prefer symmetrical figures over asymmetrical figure (such as the image below) ­ ­ Evolutionary significance​ ­ ability to detect may aid in survival (if you see a tiger you run away vs if you see a rock that is NOT symmetrical. Basically we don’t need to attend to things that are not symmetrical) 6. Law of Good Continuation ­ The tendency to connect elements in a way that makes the elements seem continuous or flowing in a particular direction ­ BOTTOM UP PROCESSING 1. Distinctive features theory 2. Recognition by components theory 3. Template­matching theory 4. Prototype theory 18 How do we perceive and recognize stimuli according to distinctive features theory Distinctive Features Theory ­ Gibson (1969) ­ All complex perceptual stimuli are composed of distinctive and separable attributes called ​features ­ Distinctive features are cuse that allow observers to distinguish one object from another ­ According to this theory, pattern recognition is accomplished by mentally assessing the presence or absence of critical features (achecklist​...does it have this features, yes or no) Distinguish local and global features of Navon stimuli. What did Navon’s 1977 experiment utilizing the stimuli reveal about the processing of local and global features ➢ Prioritizing features ○ Navon, 1977 ○ Global features​ = the letter the the small letters make up ○ Local features​ = the letters within the big letter ○ Study using Navon figures demonstrated that global features are processed prior to local features ■ Could tell b/c if the local feature conflicts with the global feature it didn’t change the reaction time ■ However if told to name the local feature it took more time if it’s inconsistent with the big global feature How do we identify patterns according to the recognition by components theory (Biederman) Be able to define geons and explain their role in the pattern recognition process. Recognition by Components Theory ­ Biederman (1987) ­ Describes the pattern recognition process in terms of how people recognize 3­D objects ­ by identifying basic features that comprise the objects ­ These basic elements are composed of an alphabet of 36 primitive shapes, called ​ geons ­ GEONS ­ Geometric ions ­ 36 primitive shapes that are the building blocks for identifying 3­D objects ­ Critical pattern recognition because can be rotated in three dimensions and create an unlimited number of impressions on the retina ○ People identify an object by noticing edges and geons that fit the edges and then rely on long­term memory of objects with that configuration of geons 19 Describe template matching theory and how past experience is used in the pattern recognition process. Template Matching Theory ­ Practical for machines but not humans ­ Assumes we have an unlimited number of patterns stored­­literal copies corresponding to every object we have experienced ­ Patterns are labeled with the name of the object and can be matched to a new instance of the object Describe a strength and a weakness of this theory. STRENGTH: This theory works well when objects can be easily discriminated ➢ Describes the pattern recognition used by machines to analyze checks WEAKNESS: This theory is NOT practical for human pattern recognition ➢ Too many possible patterns ➢ Inefficient ➢ Can’t account for recognizing new objects What is a prototype How does pattern recognition occur according to prototype theory Prototype ­ An average (or typical instance) of many different views of an object Prototype Theory ● Pattern recognition occurs when the features of the object to be recognizes overlap in some way with the features of the prototype ● Ex. If we see a weird looking table we can still recognize it ● Addresses some of the limitations otemplate matching theory ○ Does not need to be an exact match between object and prototype ○ Does not require storage of patterns for every possible view of an object How do the results of the experiment with the Identikit faces (Solso and McCarthy, 1981) support the ecological validity of this theory Ecological validit = corresponds to how people operate in the real world ● Solso and McCarthy (1981) ● Created prototypical faces using Identikit ● Also created exemplars that varied in degree of similarity to prototype ● During learning phase, participants saw exemplars (but not the actual prototypes) ● Later (both immediately and 6 weeks later), participants had to judge whether faces had been seen before ○ Participants were confident that they had seen prototypes before (which they had not see) ○ Important because it suggests that when we see faces we extract faces and making a “prototype” to map and recognize people 20 TOP­DOWN PROCESSING ● The mechanism by which expectations, knowledge, and context guide perception ● Allows us to behave more quickly than we could with bottom­up processing alone ● Important for speech understanding (auditory) ○ Context matters fphoneme​ perception: a perceptually distinct sound unit, but the simplest one ■ The *eel is on the shoe ● Participants heard “heel” ■ The *eel is on the axle ● Participants heard “wheel” ■ * = (a little cough as the rest of the word is said) Describe the symptoms of pure word deafness. ● Usually because of a tumor or stroke ● Patients are unable to understand spoken speech but can hear, read, speak, and write How is this problem related to top­down processing ➢ Relates to top­down processing because these people are unable to use their knowledge of language to interpret the physical stimulus of speech What is the word superiority effect Explain how it is tested. Word­Superiority Effect ● People are better at recognizing letters when they are embedded in real words than when those letters are seen in random strings of letters or when the letters appear alone ○ FONGHGTAEW ○ FOGHATNEW ● Paradigm to study word­superiority effect (Reicher, 1969) ○ Participants more accurate at identifying presence of a letter when it is within a word than when presented alone How does context facilitate pattern recognition when a person is reading ● Reading requires pattern recognition ● Reading depends on top­down processing ○ Skilled readers do not read every letter of every word but instead use context to derive meaning ■ Shape of word ■ Grammar of sentence ■ Theme of passage FACE RECOGNITION ● Top­down and bottom­up ● Important for social interaction ● Evidence in early life suggests innate biological mechanism allows facial recognition ○ Infants only a few hours old prefer mother’s face ○ 2­3 week old infants can recognize and imitate mouth gestures without explicit reward (baby watching person, makes the same faces) Describe the high amplitude sucking procedure and how it is used to assess face preferences in very young infants. Face recognition by infants ● High amplitude sucking procedure ● When infants engage in high­amplitude sucking (HAS) a sound or image is presented ○ Babies learn that HAS can change the stimulus (a sound or a picture) 21 ● Infants presented with 4 faces and then a composite that averaged the 4 similar faces or 4 new faces ○ Longer time spent looking at composite of familiar faces (not sucking to change picture) ● Explains the preference for mother’s face neonates have hours after birth ○ Newborns store a composite of faces in memory ○ Because they see mother frequently, her face makes a large contribution to the composite How do the results suggest infants are able to recognize faces ➢ Suggests that infants are able to recognize faces because on familiar faces they don’t suck to change the picture! Describe the facial prototype hypothesis of how humans recognize faces. ● Hypothesis​: humans have an inherent understanding of the structural organization of faces (the facial prototype) and recognize faces by encoding/retrieving according to this prototype ○ All faces have same set of parts ■ Eyes, nose, mouth ○ All faces appear in the same basic configuration ■ Nose centered in face, above mouth and below eyes ○ Facial prototypes allow us to process faces in holistic, gestalt manner What is the basic finding regarding the ability to recognize inverted faces What does this suggest about the facial recognition process (think about the Thatcher illusion) ● We do not have a prototype for inverted faces ○ Lack of experience with inverted faces ○ Facial recognition of inverted faces is poor ■ We can analyze component features but cannot maintain configurations of these features to holistically process the face (what it suggests) The Thatcher Illusion ● Upside down faces may look the same even if eyes and nose and mouth are different ● Evidence that we have a facial prototype ● When it’s inverted we can’t tell Describe the cross­race effect. ● People have difficulty recognizing the faces of people from a different race ● Not just as a result of having more experiences with faces of own race ○ White people in Singapore are just as bad at recognizing Asian faces as white people in Canada ● May reflect that we develop an expectation of what the configuration of a face is supposed to look like (our facial prototype) based on experience with our own­race faces ● People use features such as hairstyle and color to identify race ● MacLin & Malpa

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Chapter 17, Problem 17-97 is Solved
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Textbook: Engineering Mechanics: Statics & Dynamics
Edition: 14
Author: Russell C. Hibbeler
ISBN: 9780133951929

This textbook survival guide was created for the textbook: Engineering Mechanics: Statics & Dynamics , edition: 14. Since the solution to 17-97 from 17 chapter was answered, more than 268 students have viewed the full step-by-step answer. Engineering Mechanics: Statics & Dynamics was written by and is associated to the ISBN: 9780133951929. This full solution covers the following key subjects: cord, directed, Force, prob, upwards. This expansive textbook survival guide covers 22 chapters, and 2358 solutions. The answer to “Solve Prob. 1796 if the cord and force P = 50 N are directed vertically upwards” is broken down into a number of easy to follow steps, and 16 words. The full step-by-step solution to problem: 17-97 from chapter: 17 was answered by , our top Engineering and Tech solution expert on 11/10/17, 05:20PM.

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Solve Prob. 1796 if the cord and force P = 50 N are