By K. Kasim. Charter Oak State College.

For a rectangular solid buy levitra 10 mg amex, Ic 5 (m/12) (a2 1 b2) discount 20 mg levitra with mastercard, where a and b denote the lengths of the sides of the solid in the plane of motion. Examples of rigid objects that have planar symmetry (a) and those that do not have any plane of symmetry (b). Mass moment of inertia with respect to any other point, say point O, can be found by using the geometric relation: Io 5 (x 2 1 x 2) dm 5 Ic 1 mr2 (4. Earlier in the chapter, we found that the mass moment of inertia of a slender rod with respect to one of its ends was given by the following relation: I 5 Io 5 mL2/3 33 Using Eqn. Mass moment of inertia is an entity that readily applies to three- dimensional geometries, as we shall see later in the book. In three di- mensions, mass moment of inertia with respect to center of mass has nine 100 4. Bodies in Planar Motion components that can be organized into a 3 3 3 symmetrical matrix. That means that of the nine components only six are independent; I23 52I32, and so on. If O is a point that is fixed in a reference frame which is stationary with respect to earth, then vO 5 0. Furthermore, if the plane of motion coincides with a plane of sym- metry of the rigid body, then I13 5 I23 5 0. One final comment about the moment of momentum of a rigid body: because the rate of rotation of all points in a rigid body is the same, mo- ment of momentum is called angular momentum. The symbols Mo and Mc represent, respectively, the resultant moment of external forces about point O and the center of mass. When a rigid object undergoes planar motion, we have seen that its moment of momentum (angular momentum) can be expressed by the fol- lowing simple equations: Ho 5 Io v e (4. It is similar in structure to the equation governing the motion of center of mass, recapitulated below: m ac 5 F (4. The re- sultant external force determines the path of the center of mass during motion, whereas the resultant external moment is responsible for a change in the angular velocity of a rigid body undergoing planar motion. In the following, we present a number of examples that il- lustrate the use of these equations. Let f be the angle that the radial line of the disk passing through point O makes with the verti- cal axis. These forces are the gravitational force 2mg e2 acting at the center of mass of the disk and the reaction force (F1 e1 1 F2 e2) ex- erted by the pin at point O on the disk B. The only moment acting on the disk is the moment of the gravitational force, and through vector multi- plication it can be shown to be given by the following equation: M 52mgr sin f e3 (4. Conservation of angular momentum with respect to point O yields: (3mr2/2) a 5 (3mr2/2) (d2f/dt2) 52mgr sin f (d2f/dt2) 52[2g/(3r)] sin f (4.

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There has been a very substantial change over the last decade and now much greater professional attention is being paid to people who have these symptoms purchase levitra 20 mg amex. Fatigue Fatigue or tiredness is one of the most debilitating symptoms of MS and one that worries many people effective 20mg levitra. Up to 90% of people with MS experience overwhelming tiredness at least some of the time. Fatigue in MS is often associated with: • heat (or being hot) (see Chapter 6); • activity – using motor skills, or being mobile; • sleep disturbances; • particular mood states (such as depression – see later section); • some cognitive problems that may occur in MS (see later section). Some argue that the best way to manage fatigue is to consider it as a symptom arising from several different sources and thus requiring different techniques to manage it. We could distinguish what we might call: 78 FATIGUE, COGNITIVE PROBLEMS AND DEPRESSION 79 • normal fatigue resulting from everyday exertion etc. Management of fatigue Although it is important that your symptom is recognized as genuine by medical and other healthcare staff (which has been a problem in the past), you will probably have to manage many of the day-to-day aspects of fatigue yourself, for drug therapies (see below) are often only partially successful. Self-help • Identify activities that appear to precede the fatigue and avoid them whenever possible. However, ‘fatigue management strategy’ tends to be a complicated business, taking a lot of energy in itself to think through all the possibilities that might occur. Professional support Specific and carefully planned exercise programmes have been found to reduce feelings of fatigue, but only temporarily. Behavioural therapy can help to alleviate other psychological symptoms that might exacerbate the fatigue, but these non-drug professional approaches have not been successful so far for most people with MS over the medium and longer term. Drugs Some drugs have helped, the two most well known being magnesium pemoline (Cylert), which stimulates the CNS, and amantadine hydro- chloride (amantadine; Symmetrel), an antiviral agent. It has also been suggested that fluoxetine (Prozac) may help in managing MS fatigue. Some antidepressants, particularly those that have a low sedative effect, may help the tiredness even if you are not clinically depressed. Beta-interferon drugs may have some effect on fatigue if, indeed, they help the immune system. Fatigue may be one thing that affects cognition, although it is still not yet clear exactly how this happens. Some people with MS feel fatigued almost simultaneously as they notice problems with their memory or concentration (see below). Self-rated fatigue is linked with certain forms of memory problems, as well as reading comprehension.

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This should be done a minimum of two weeks in advance so that there is still time to correct slides and iron out flaws in your delivery technique cheap 20 mg levitra with visa. For the longer talks you should sit with your manuscript and visual aids and go through the talk and slides and time how long it takes generic levitra 10 mg otc. You should do this several times before your talk and you should do it every time you are going to lecture, even if it is the same talk. When rehearsing in this way, always go through the slides as you would at the actual presentation. Presentation You are going to be nervous when you stand up in front of an audience to talk, particularly the first time. Although the more experienced lecturers may not give this impression, you can guarantee that there will be a degree of apprehension. Under no circumstances should you resort to pharmacological help to allay this apprehension. It gives the impression that you don’t know your subject and also keeps your head down and encourages you to mumble. Your head must be up, talking to the back row and, in order to do this, you must know and have learned what to say. Turn to them to refresh yourself as to the next point, then turn back to talk to the audience. The only reason why people want to read the manuscript is because they are frightened they might forget to say something. This is totally irrelevant because nobody in the audience would know you were going to say it anyway. If you do suddenly remember that you were going to say something five minutes ago, ignore it; do not go back to it. This does not mean that you shouldn’t have the full script available, and even refer to it very briefly from time to time, but the professional doesn’t need one. Visual aids The most important thing to remember about visual aids is that they are aids. Very clever things can be done with them these days, 15 HOW TO PRESENT AT MEETINGS but they must not be allowed to take over. Whatever you use, some basic points apply: • Give the impression that you know your slides, so be confident and know what is coming next. So remember, lectures take time to prepare and if your preparation has been meticulous and you have rehearsed your talk with colleagues and sought their advice, the lecture really won’t be a problem. Summary • The key to a good lecture is preparation and rehearsal • Check the content of the meeting at which you are going to talk, the subject and timing • Understand the audience in order to select the right level at which to pitch your presentation • Think carefully about the title and the content of your talk • Select and arrange information according to the audience and time given • Rehearsal is mandatory 16 3 The three talks MAL MORGAN Hospital medical practice would be regarded as strange by many people and particularly the treatment of emergency cases.

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