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The solid spindle AB has a diameter ds 5 1.75 in. and is

Mechanics of Materials | 6th Edition | ISBN: 9780073380285 | Authors: Ferdinand Beer ISBN: 9780073380285 142

Solution for problem 3.40 Chapter 3

Mechanics of Materials | 6th Edition

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Mechanics of Materials | 6th Edition | ISBN: 9780073380285 | Authors: Ferdinand Beer

Mechanics of Materials | 6th Edition

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Problem 3.40

The solid spindle AB has a diameter ds 5 1.75 in. and is made ofa steel with G 5 11.2 3 106 psi and tall 5 12 ksi, while sleeve CDis made of a brass with G 5 5.6 3 106 psi and tall 5 7 ksi. Determine(a) the largest torque T that can be applied at A if the givenallowable stresses are not to be exceeded and if the angle of twistof sleeve CD is not to exceed 0.3758, (b) the corresponding anglethrough which end A rotates.Fig. P3.39 and P3.40

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UNDERSTAND THE CONCEPT OF AROUSAL First, let’s begin with the technical details. Arousal is defined as the activation that occurs before or during a behavior. Types: This can occur on two different levels, namely physiological (the autonomic nervous system) and psychological (the brain, or any part outside of the central nervous system). This can manifest with increased heart rate and shaking hands (physiological), or in psychological symptoms with feelings of anxiousness or overthinking the situation. To help you remember this, picture the day we played Operation in class. When the room was relatively quiet, winning Operation was an easy enough task. Though when the heavy metal music started, the game sort of fell apart. Too much stimulation was present at one time. This relationship can be modeled with an upside down U shaped curve. But why does all this matter Well, anxiety on a small scale can be good a good motivator, which leads to the conclusion of arousal being a motivator. However this only stays true on a small scale; once the anxiety climbs too high, too much cortical activity leads to the fight or flight response in full fury. When we are not at our optimal level of arousal (different for each person) we perform motivated behavior to correct the imbalance. Conclusion: Now, we cannot directly measure motivation, but perhaps motivation can be indirectly measured through arousal A caveat to this however, is that some individuals are not as easily stimulated by the same stimulus, or can be overstimulated as can be the case with autistic individuals. Keep in mind that every task for every individual has a different inverted U shape, and that behavior never occurs in it of itself, but rather within context. Reticular Formation There are two main kinds of arousal: behavioral, cortical, and biological. Behavioral arousal is the behavior you can see in studies through an individuals actions. This is not the most accurate form of measuring arousal and behavior can be controlled on some level. For example, when prey is cornered, it freezes even though it’s autonomic nervous system is on full blast. The autonomic nervous system (ANS) is in charge of smooth muscles, glands, and cardiac tissue, whereas the somatic nervous system (SNS) is rather in charge of muscular reflexes. Biological arousal is again looked at within the realm of the autonomic nervous system, although divided into the sympathetic and parasympathetic system. The sympathetic is the fight or flight, making the sole goal of the body to be survival. Unnecessary processes stop, such as digestion and sexual arousal (no one needs sex when in a life threatening situation!) and processes which boost the senses kick into high drive with increased heart rate and expanded pupils. The parasympathetic is known as the rest and digest stage, where the high drive processes slow and your body resumes normal working state. To remember this, you can think of the sympathetic system as the resourceful one which gets you out of dangerous situations. Here is a rough diagram which demonstrates how closely linked the two systems are: Cortical arousal is going to be a bit more technical. We will begin with the various types of arousal waves: alpha waves are present at unfocused attention (8-12 Hertz), beta waves are focused attention (3.5-7.5 Hertz), theta waves when falling asleep and during REM sleep (13-30 Hertz), and delta waves when in deep sleep (less than 4 Hertz). These waves can be seen with an EEG, or electroencephalogram which can measure the average activity level of the neuron population. When aroused, the neuron firing becomes asynchronous, or more and more irregular. Two scientists named Moruzzi and Magoun continued a study by Bremer (who sliced cat’s brains methodically and studied brain activation with EEGs) and focused on the pons gland. Through their cooperative efforts, they discovered the reticular activating system, or reticular formation. Descending reticular formation deactivates arousal, whereas ascending reticular formation arouses the brain when surprised. Dreams Sigmond Freud is perhaps one of the most important individuals to consider when talking about dream theories, in particular the psychodynamic model. He believed the mind was divided into three sections: the Id (primal, animalistic part), the Ego (the rational part which balances the Superego and Id), and the Superego (the moral part of our minds). Freud believed the Id is the most truly unconscious state, the state where everything we try to bury comes out, and that dreams are a manifestation of that unconscious. Though these thoughts come directly from the Id, they are somewhat transformed to protect us from the pure Id thoughts. Or, more simply, dreams can just be a playback of the day, clearing through mental residue. Other dream theories include: the evolutionary and extra theories. The evolutionary theory grasps on the prospect of most of our dreams being negative in content, which could provide our brains with practice in dealing with future threats. The synthesis model suggests that dreams are simply your cortex attempting to make sense of random brain stem firing, whereas the consolidation theory hypothesizes that dreams solidify memories through “playback”. Drives The most basic definition of a drive involves some impulse based on need, due to some variation away from homeostasis. This can be represented in terms of glucose levels (craving sugar to raise glucose), fluid levels (needing to drink or urinate), and temperature control (putting on a sweater or shivering). Drives both activate and direct our behaviors with a certain persistence and a certain vigor, which is motivation! There are two types of drives, regulatory and non-regulatory. Regulatory drives are the ones which, logically, involve regulation for individual survival. Non-regulatory drives have other purposes, such as sexual arousal, and parenting instincts. The Central State Theory (CST) speculates as to whether there is one central-drive system, one system which drives us to do everything we do. Technically speaking, if such a “thing” did exist in our brain, it would have to be able to both identify that our bodies are no longer in homeostasis and somehow correct that imbalance through bodily adjustments. This area of the brain is known as the hypo-thalamus, located just under the thalamus. The Hypo-Thalamus The most general functions of the hypo-thalamus (HT) can be remembered through the four F’s: Feeding, Fight, Fear, and Sex (think that one through…). The first three are about maintaining homeostasis, whereas the latter is a Species-Typical behavior. Emotions can be represented through motor functions in the face and changes in the chemistry of the HT, which provokes changes in your limbic system. The HT has two “arms”: the autonomic nervous system and the endocrine system; it also connects to the reward zone of the brain, which can explain why we feel satisfied after eating and having an orgasm. The Hypo-Thalamus is divided into three zones. The pre optic zone plays a huge role in temperature control, which is all about homeostasis. The lateral periventricular zone is theorized to be a feeding center, as when it is over-stimulated we get overfeeding, whereas lesioning it gives anorexia, as there is no longer a reward for eating. The medial periventricular zone can also be broken into three regions, though only one is being focused on in this course. The supraoptic region suggest support for neoteny (instinctively wanting to nurture baby-like things) and circadian rhythms. Final Notes Sexual desires and motivational systems can be found in the bundle of week 9 notes, which I will be including in this review. As it is the most recent week, it will be the freshest in mind, and as the most important section I will include the bundle of notes rather than a summary. Week 9: Sexual Behavior Hormonal Control of Sexual Behavior of Laboratory Animals Females: • In some species, the female’s role during the act of copulation is merely to assume posture • Postures are adaptive in that they promote sexual reproduction Lordosis • - To give you an idea of the posture, the female’s back is curved in a concave up form, looking roughly like a ‘U’, with the tail close to the back - Credit of the photo goes to wikipedia.com - A female rat will be more predisposed to exhibit this behavior during the estrous cycle - The end game is lordosis is to let the male rat intermit more easily, whereas the male end goal is to ejaculate - For exam two, make sure to study the male rat’s brain during the act of sexual intercourse - The hypothalamus is involved in species typical behavior, which happens to include sexual behavior, as triggered in the medial pre optic area • Note: quadrupedal brains are in a different orientation due to the evolution of humans, from quadruped to biped, thus orienting our brain about 90 degrees counterclockwise - Smell can be regarded as a key element to sexual drive, as there happens to be an olfactory domain in the reproduction system Male • In a male rat’s brain, specifically the olfactory bulb and vomeronasal organ, olfactory receptors can sense fatty acids released by the female rat’s vagina during certain stages of ovulation. • In humans, the olfactory organ’s axon stems up to the area behind our eyes, which may suggest that humans have moved from olfactory cues to visual cues • The medial amygdala is in charge of detecting whether experiences will be pleasurable or not, which plays a big role in a male rodent when he smells a female rodent. When the medial amygdala or MPA (medial pre optic area) are lesioned, sexual behavior is abolished, due to it no longer being connected to the medial pre optic area, which is the orchestrator of sexual reproductive behavior. -The amygdala and central tegmental field will also release the Fos protein during mating. High amounts of this protein indicate high transcription and translation rates, which can indicate an increase in activated target organs. This is the process which is measured when looking at neuron releases. • Castration can lead to reduce activity in the amygdala and MPA, due to lowered testosterone levels, which can however be combatted by testosterone injections. - This all leads to the conclusion that hormones motivate sexual behavior! - It is interesting to note that if you castrate rapists (old treatment), they will still commit rape, which indicates that rape is not a sexual behavior. They may become less aggressive, but will still continue. This is countered with pedophiles, who show decreased sexual behavior, indicating that their behavior is indeed sexually driven. - The Periaqueductal Grey and nPGi can essentially “turn off” mating, however the MPA can “turn off” that area, giving two pathways to sexual behavior, with one pathway increasing sexual behavior and the other counteracting it. This has an inhibitory effect on penile erection. • The pathway we must know for the exam is the Medial Amygdala turning off the nPGi • It is interesting to note that in depressed individuals, the nPGi is turned up which turns off sexual drive • Medial Preoptic Area (male only)—> Medial Amygdala (ends cycle) or Periaqueductal Grey —> Nucleus Paragigantocellularis (nPGi)—> Tactile information from copulation —> Central Tegmental Field (releases Fos) —> Medial Amygdala, which completes the loop Female • The main area of sexual motivation in males is the MPA, however in females it is the VMH, or Ventromedial Nucleus of the Hypothalamus (female only) • For the exam, make sure to know the overlap in both male and female systems, however make sure to also know the contrast! • It is important to note that although we spoke of this system step-by-step, much of this feedback is received at the same time. Olfactory and tactile and central tegmental field feedback occurs congruently. • Let’s say you give a female rodent the equivalent of male castration. The removal of the ovaries will over time abolish sexual impulses • Inhibition is not involved in the female brain, only activation • VMH —> medial amygdala —> can go back straight to the VMH and end the chain, or goes to the PAG of the midbrain —> nPGi of the medulla —> can go to both the medial amygdala and VMH • When beginning the mating sequence, the male will approach tentatively and will smell the female. If she smells receptive, he will then lick her genitals which will in essence “prime” her through the stimulation of the sexual brain circuit. • The end game for this activation of the nPGi is lordosis, rather than penile erection and ejaculation - Remember to study the diagrams, there is no way around that! Do it like a story, start at the beginning and follow the arrows, noting the colour of the arrows to indicate activation or inhibition. - All of this again goes to show that the thalamus controls sexual behavior Parental Behavior - If you really think about it, parental behavior is an anomaly. It slows down the parents and makes them more susceptible to injury - Maternal behavior involves the nucleus accumbens, as it received dopamine which is reinforcing. Thus maternal behavior is rewarding. If lesioned, maternal behavior may decrease • This proved that there are neural substrates of parental behavior - Remember, regulatory drives are driven by survival, versus un-regulatory behaviors like sexual intercourse which are not essential to a species’ survival. - Bacteria and viruses could be the reason for maternal behavior and sexual drive, as it would lead us to promote immune system defense against bacteria and viruses - Short - term lack of sleep does not result in death, however long-term... - Here is an example of maternal behavior non-conducive to personal survival: A female rat will usually give birth to many pups at a time. They are also hungry to no end, and the mother spends most of her time feeding. However, due to this nutrient loss, the mother will lick the pup’s genitals and drink the urine to replenish the lost nutrients. • This suggests that regulatory and non-regulatory drives may overlap in some form - Interestingly, an overlap has been shown between levels of oxytocin and autism, though oxytocin is mostly know as the love hormone. Could this mean that oxytocin injections could aid those with autism with their social skills

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Chapter 3, Problem 3.40 is Solved
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Textbook: Mechanics of Materials
Edition: 6
Author: Ferdinand Beer
ISBN: 9780073380285

This full solution covers the following key subjects: angle, tall, sleeve, PSI, made. This expansive textbook survival guide covers 11 chapters, and 1493 solutions. Since the solution to 3.40 from 3 chapter was answered, more than 400 students have viewed the full step-by-step answer. The full step-by-step solution to problem: 3.40 from chapter: 3 was answered by , our top Engineering and Tech solution expert on 11/15/17, 02:40PM. This textbook survival guide was created for the textbook: Mechanics of Materials, edition: 6. Mechanics of Materials was written by and is associated to the ISBN: 9780073380285. The answer to “The solid spindle AB has a diameter ds 5 1.75 in. and is made ofa steel with G 5 11.2 3 106 psi and tall 5 12 ksi, while sleeve CDis made of a brass with G 5 5.6 3 106 psi and tall 5 7 ksi. Determine(a) the largest torque T that can be applied at A if the givenallowable stresses are not to be exceeded and if the angle of twistof sleeve CD is not to exceed 0.3758, (b) the corresponding anglethrough which end A rotates.Fig. P3.39 and P3.40” is broken down into a number of easy to follow steps, and 91 words.

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The solid spindle AB has a diameter ds 5 1.75 in. and is