Gravitational force: An overview

Gravitational force: An overview 1.0 Introduction 1.1 What is gravitational force? Gravitational force is defined as a force of attraction which exerts between two objects with mass. It pulls two objects that have mass. (Gravitation and Gravity n.d.). 1.2 Background Information 1.2.1 The discovery of gravitational force One day, Newton was sitting on his garden and observing the falling of an apple from a tree. A sudden inspiration appeared in his mind. There must be a force exerted on the apple since the apple accelerated while falling down from the tree with zero initial velocity. The force is then called â€Å"gravity† and the acceleration due to the force is called â€Å"acceleration due to gravity† (Sir Isaac Newton: The Universal Law of Gravitation n.d.). 1.2.2 Effects of gravitation on planets If the force of gravity exerts at the top of the trees and mountains, then it must exerts all the way to the orbit of the moon. It is expected that the orbit of the moon around the earth results from the gravitational force as the acceleration due to the gravity can change the velocity of the moon in such a way it followed an orbit around the earth (Sir Isaac Newton: The Universal Law of Gravitation n.d.). 2.0 The Universal Law of Gravitation 2.1 Keplers law of gravitation Keplers Third Law states that the ratio of the cubes of their mean distances from the Sun is same as the squares of the periods of any two planets orbit about the Sun. P represents the time taken for one revolution about the Sun and R represents the distance between the planet and the Sun. The equation indicates that the period for the planet to orbit the Sun is proportional to the radius of its orbit. (Johannes Kepler: The Law of Planetary Motion n.d.). However, the accurate measurements on the orbits of the planets showed that they do not precisely follow Keplers laws. The validity of the Keplers law is corrected by Newton. The mass of the Sun is extremely greater than any other planet. Thus, the force of attraction between planets will be small compared to the force due to the Sun (Sir Isaac Newton: The Universal Law of gravitation n.d.). 2.2 The law of universal gravitation Law of universal gravitation states that every particle in the universe attracts each another with a force that is proportional to the product of their masses and inversely proportional to the distance apart squared. This force exerts along the line of centers joining the two particles. The magnitude of the gravitational force can be calculated using the formula: Fg = GMm Fg is the magnitude of the gravitational force r ² G is universal gravitational constant M and m are the masses of the two particles. r is the distance between the two particles. The universal gravitational force is also named universal constant as it is expected to be constant at any times and places. Therefore, it is universally characterized the intrinsic strength of gravitational force (Sir Isaac Newton: The Universal Law of gravitation n.d.). The gravitational constant is very small since we are unaware of the existence of the force of attraction between objects. The accepted value is G = 6.67 x 10-11 Nm ²/kg2. Based on the equation, the greater the distance between two masses, the smaller the gravitational force (Universal gravitation and weight n.d). 3.0 Gravitational fields Gravitational field is defined as the gravitational force felt by a discrete particle in a particular area (Fowler 2006). 3.1 Field strength Gravitational field strength is defined as force, N per unit mass, kg. The definition of gravitational field strength is derived from the Newtons second law, ÃŽ £F=ma. By making acceleration, a, as a subject and then substitute acceleration, a with gravitational field strength, g, and we would obtain a formula, g = F/m. F represents the gravitational force, N whereby m represents the mass of an object, kg. Gravitational field strength close to the earths surface is the same as the gravitational acceleration, 9.8Nkg-1. When the force is not given, gravitational field strength can be calculated by using the formula, g = GM/r ². This formula can be obtained by the substitution of the two equation, F = mg and F = GMm/r ². Hence, resulted in the formation of the equation, g = GM/r ². The greater the value of g, the greater the gravitational field strength (Universal Gravitation and Weight n.d.). 3.2 Principle of superposition In terms of gravitation, principle of superposition refers to the total force of an object. Total force is the addition of all the vectors due to the gravitational fields of force acting on the object (Fowler, 2006). Superposition refers to the masses which interact with each other. To find the total force, we have to find the gravitational force for each mass by using the formula, Fg = GMm/r ². Finally, add up all the forces by using vector addition method (Forces and Fields n.d.). 4.0 Future of Gravitation Einstein theorized that gravity can be explained by the curvature of space time.  Space time is warped by the mass and energy inside of it but not flat. Objects travel in straight line do not hold by mysterious force but follow the curves in space time. The objects move in straight lines along four-dimensional space time but move in elliptical circles in three-dimensional space. Light appears to travel in straight lines although it is actually bent, curved and changed by the fabric of space time. Although it looks like straight out in front of us, it is actually around the corner of the sun because the space time warp morphs the light. We see only the result of the light that is being bent around the sun. This can not be tested since the sun is shining us right in the eyes and we cannot see the stars.  However, it is possible to test out this theory during a total solar eclipse. We are constantly orbiting the sun so we are able to observe the changes of the movement of the star i n orbit (Space Time: The Fabric of the Universe n.d.). 5.0 Conclusion In conclusion, based on the acceptable Newtons gravitational law of gravitation, gravitation is a mutual force. Every particle in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Therefore, gravitational force is depends on the masses of the bodies and the distance between the two bodies. Reference List Forces and Fields n.d., viewed 29 July 2009, http://electron9.phys.utk.edu/phys136d/modules/m4/efield.htm Fowler, M 2006, Gravitational Field, viewed 29 July 2009, http://galileo.phys.virginia.edu/classes/152.mf1i.spring02/GravField.htm Gravitation and Gravity n.d., viewed 29 July 2009, http://alex.edfac.usyd.edu.au/Methods/Science/studentwork/MassoftheEarth/gravitationandgravity.htm Johannes Kepler: The Laws of Planetary Motion n.d., viewed 29 July 2009, http://csep10.phys.utk.edu/astr161/lect/history/kepler.html Newtons Law of Gravitation n.d., viewed 29 July 2009, http://theory.uwinnipeg.ca/physics/circ/node7.html Sir Isaac Newton: The Universal Law of Gravitation n.d., viewed 6 June 2009, http://csep10.phys.utk.edu/astr161/lect/history/newtongrav.html Space Time: The Fabric of the Universe n.d., viewed 29 July 2009, http://www.astronomy.pomona.edu/Projects/moderncosmo/alexs%20page%201.html Universal Gravitation and Weight n.d., viewed 29 July 2009, http://dev.physicslab.org/Document.aspx?doctype=3filename=UniversalGravitation_UniversalGravitationWeight.xml Intellectual Disability: Causes and Conditions Intellectual Disability: Causes and Conditions Assessment Demonstrate knowledge of causes and associated conditions related to intellectual disability Outcome 1: Define Intellectual Disability Task 1 1.1 Give 2 definitions of intellectual disability in accordance with a recognised source. Follow prescribed APA format when citing sources. Definition 1: Intellectual disability is a disability characterized by significant limitations in both intellectual functioning and in adaptive behaviour which covers many everyday social and practical skills. This disability originates before the age of 18. Source: World Health Organization. Definition 2: Intellectual disability means a significantly reduced ability to understand new or complex information and to learn and apply new skills (impaired intelligence). Source: World Health Organization. 1.2 Using a definition of intellectual disability give 2 explanations of how this impacts on the persons adaptive skills: The person finds it hard to understand and follow social rules and customs and obeying laws. The person finds it difficult to perform the daily activities which include feeding, bathing, dressing, occupational skills, and navigational skills. Using a definition of intellectual disability give 2 explanations of how this impacts on the persons cognitive ability. A person is not able to think, reason, and solve problems or make decision like what to say while answering the telephone or talking to another person. A person is not able to concentrate, learn new things and does not have the ability to talk or write, resulting in the inability to live independently. Reference: FAQ on Intellectual Disability, American Association on Intellectual and Developmental Disabilities. Outcome 2: Describe the outcomes of intellectual Disability Task 2 2.1 Give 2 examples of causes of intellectual disability that occur before birth and describe two [2] main characteristics of the effects. Example1: Fragile x Syndrome. Source: Bray, Anne, Definitions of intellectual disability, [Donald Beasley Institute, 2003] Main characteristics: If the mother does not follow a low phenylalanine diet before birth then the infants will have a low birth weight and grow more slowly than other children. The child will have heart defects or other heart problems, like abnormal small head size and behavioural problems. Example 2: Downs Syndrome Source: Bray, Anne, Definitions of intellectual disability, [Donald Beasley Institute, 2003] Main characteristics: It is caused by a random error in cell division and results in abnormality in physical characteristics like small chin, round face and almond eyes. The baby will have shorter limbs, protruding or oversized tongue and also have obesity problems. 2.2 Give 2 examples of causes of intellectual disability that occur during or immediately following birth and describe 2 main characteristics of the effects. Example 1: Premature Birth. Source: World Health Organisation, International Classification of Disability, and Health. Main characteristics: It happens when mothers smoke cigarettes, drink alcohol or use illicit drugs which results in unresponsive reflexes and problem in breathing. If the mother suffers from stressful life events, such as death of a loved one or domestic violence which results in slow heart rate or difficult feeding. 2.3 Give 2 examples of causes of intellectual disability that occur during childhood years and describe the impact on the day to day support needs of the person. Example 1: Malnutrition Source: Diagnostic and Statistical Manual of Mental Disorders. Impact: The person will have problems in doing his daily activities like going to school or understand what is happening around him or eating his food at the time and taking his medication. He won’t be able to concentrate in class and will often feel depressed. He will need words of encouragement from his teachers and parents. His daily activities should be monitored and ensure to keep health appointments with the physio, social worker and therapists. Example 2: Brain injuries. Source: Diagnostic and Statistical Manual of Mental Disorders. Impact: The person will have difficulty with memory tasks like math facts or spelling words. He may not be confident in school will be easily frustrated. He may seem to remember information one day and forget it the next. He will need support in bathing, grooming, and needs reminding of personal hygiene like washing his hands after using the toilet and brushing his teeth. Help from support groups and agencies are also necessary. Outcome 3: Describe conditions frequently associated with intellectual disability. Task 3 Condition 1: Foetal Alcohol syndrome Causes: Mothers drinking during pregnancy leads to foetal alcohol syndrome. Miscarriage, stillbirth premature birth and small birth weight are all associated with it. When a pregnant women drinks alcohol, it easily passes across the placenta to the fetus which can harm the baby’s development. Main Characteristic 1: Children with FAS have distinct facial features including small and narrow eyes, a small head, a smooth area between the nose and the lips and a thin upper lip. Main characteristic 2: They also have hearing and ear problems. Their immune system are also weak due to FAS and they have issues with their height and weight. Description of the Support Needs of the person with the condition: Physical Support: The person needs to be reminded when to take his medicines or needs assistance in taking his medication. They will need assistance in crossing the road and also with daily activities like bathing, grooming and brushing their teeth or putting on their shoes. They will also need speech therapist so that they can interact with their peers. Social Support: The person will need communication and social skills training for interaction with friends, teachers and others. They will need supportive activities like group work to gain confidence and independence. Regular interaction with other children will boost their self-confidence. Cognitive Support: The person will need special education teacher to teach how to talk and what words he should use while talking to someone. He will need a speech therapist to learn how to pronounce a word or say a word clearly. Condition 2: Autism Causes: It is not certain what causes ASD, but it’s likely both genetics and environment play a role. Some studies suggest that people with ASD have abnormal levels of serotonin or other neurotransmitters in the brain. Main Characteristic: 1 People with Autism will have repetitive, obsessive, and unusual behaviour. They will have difficulty in communicating with others does not speak with anyone. They will have excessive lining up of toys or objects and they also have no response to name or social responsiveness. Main Characteristic: 2 They won’t have eye contact while talking to another person and avoid bright lights, noises or physical contact. They won’t be able to understand facial expressions or understand humour or pain, unable to establish friendships and may become isolated. Description of the Support Needs of the person with the condition: Physical Support: They will need an environment which is free from noise and avoid bright lights. They will need constant supervision while doing any work or playing outside. They will need relaxation and stress management like body massage or occupational therapy. Social Support: They will need assistance in learning society rules or social behaviour using logic. They will need advice like how to interact with people and make friends. They will need opportunities for relaxation like chilling out with family and friends. Opportunities for friendships are also important for these people. Cognitive support: The person will need one on one session between him and the therapist. He will need assistance in things like reading a book or solving a math problem. If there is a changes which is made then he should be informed in a manner that makes sense to the person. Reference: FAQ on Intellectual Disability, American Association on Intellectual and Developmental Disabilities. Condition 3: Epilepsy Causes: Epilepsy can be due to severe head injury, strokes, birth trauma, brain tumours, toxins, brain infection, brain diseases, genetic condition or drug abuse.In many cases the cause is unknown. Main Characteristic 1: The person affected will have recurring and spontaneous seizures .The person may be unconscious or completely unaware of what is happening. Main characteristic 2: Some people with epilepsy simply stare blankly for a few seconds during a seizure, while others repeatedly twist their arms or legs. Seizures may be partial affecting small part of the brain or generalised, affecting whole brain. Description of the Support Needs of the person with condition: Physical Support: Making sure that the environment is safe while walking around so that they won’t get injured when seizure occurs. The environment should be hazard free. He should be monitored weather he is taking his medication at the right time or is he getting any side effects which needs to be reported to the right people. Social Support: He should be encouraged to attend school and work and needs to be reminded constantly that he should not be ashamed of his condition. He should be encouraged to maintain contact and communication with friends and co-workers. He should not be treated differently from other co-workers only because of his condition and he should be treated with respect. His dignity should be maintained during seizure episodes. Cognitive Support: He could be missing learning opportunities during seizure and might need extra teaching support. Keeping an appointment dairy will ensure that he is keeping up to date with his activities. Reference: Bray, Anne, Definitions of intellectual disability. [Donald Beasley Institute,  2003]