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Gravitational force

Gravitational force. Dr B.Kalpana. Natural phenomenon by which physical bodies attract with a force proportional to their mass. Newton's theory of gravitation Archimedes principle Gravitation force Centre of gravity. Acceleration.

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Gravitational force

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  1. Gravitational force DrB.Kalpana

  2. Natural phenomenon by which physical bodies attract with a force proportional to their mass. • Newton's theory of gravitation • Archimedes principle • Gravitation force • Centre of gravity

  3. Acceleration • Rate of change of velocity with respect to time in either magnitude or direction • Gravity is the most common accelerative force

  4. FACTORS AFFECTINGACCELERATIVE FORCES • Intensity • Duration • Rate of onset • Body area and site • Impact direction

  5. Gravity • Gravity is the force that objects exert on each other because of their masses. • Mass: a measure of how much matter an object is made of. • Matter: Anything that has mass and volume. Matter is typically a solid, liquid, or a gas. • When you drop any object (for example, a pencil), it falls to the ground. As the object falls, it moves faster and faster. • The downward pull of an object is due to gravity.

  6. Newton’s Laws of Motion • 1st Law – An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force. • 2nd Law – Force equals mass times acceleration. • 3rd Law – For every action there is an equal and opposite reaction.

  7. 1st Law of Motion (Law of Inertia) An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.

  8. Objects on earth, unlike the frictionless space the moon travels through, are under the influence of friction.

  9. 2nd Law The net force of an object is equal to the product of its mass and acceleration, or F=ma.

  10. Newton’s Law of Universal Gravitation • Any two objects attract each other with a gravitational force, proportional to the product of their masses and inversely proportional to the square of the distance between them. • The force acts in the direction of the line connecting the centers of the masses.

  11. Newton’s Law of Universal Gravitation http://scienceblogs.com/startswithabang/upload/2009/07/meet_our_second_moon/400px-NewtonsLawOfUniversalGravitation.svg.png

  12. Gravity, Mass, and Distance Mass • The more mass two objects have, the greater the force of gravity the masses exert on each other. • If one of the masses is doubled, the force of gravity between the objects is doubled. • Greater mass results in greater force. Distance • As distance between objects increases, the force of gravity decreases. • If the distance is doubled, the force of gravity is one-fourth as strong as before. • Greater distance results in smaller force.

  13. Center of Gravity (C of G) The “balance point” of the body. The point where the weight of the body acts. The point where all forces acting on the body equal zero: Linear forces must be balanced. Torques must be balanced.

  14. The location of the center of gravity remains fixed as long as the body does not change shape. If an object’s shape or position changes, the location of the Center of gravity changes. Fig 14.3

  15. As one changes the relationship of the body the C of G may even be located outside the body. Fig 14.4

  16. Placement of the Center of Gravity in Humans The location of the Center of gravity of a human in standing position varies with body build, age, and sex. Female’s center of gravity is ~ 55% of standing height Male’s center of gravity is ~ 57% of standing height

  17. Stability of the body against the gravitational force is maintained by the bone structure of the skeleton. • To maintain stability the vector sum of all forces applying at the CG must be zero!

  18. Relationship Between Weight and Mass • Weight  force of gravity on object • Force • Mass  measure of inertia of object • Amount of matter present

  19. Characteristics of Uniform Circular Motion • Tangential (linear) Velocity • Frequency • Period • Centripetal Acceleration

  20. Density and Specific Gravity The density ρ of an object is its mass per unit volume: The SI unit for density is kg/m3. Water at 4°C has a density of 1 g/cm3= 1000 kg/m3. The specific gravity of a substance is the ratio of its density to that of water. (10-1)

  21. Force on car Force on passenger Tendency for passenger to go straight Centripetal- "Center Seeking" The force or forces needed to bend the normally straight path of a particle into a circular or curved path is called the It is a pull on the body and is directed toward the center of the circle. CENTRIPETAL FORCE.

  22. Without a centripetal force, an object in motion continues along a straight-line path. With a centripetal force, an object in motion will be accelerated and change its direction. Remember Newton’s 1st Law? What is the centripetal force?

  23. Centripetal Motion 3 Important Equations v = 2pr/T Period (T) = time for 1 rev

  24. Body Mechanics • The use of one’s body to produce motion that is safe, energy conserving, and anatomically and physiologically efficient and that leads to the maintenance of a person’s body balance and control

  25. Benefits of proper Body Mechanics • Conserve energy • Reduce stress and strain to muscles, joints, ligaments, and soft tissue • Promote effective, efficient respiratory and cardiopulmonary function • Promote and maintain proper body control and balance • Promote effective, efficient, and SAFE movements

  26. Mechanics: Poor Posture • One of the main reasons that injuries occur • Means that the spine’s normal curves are exaggerated or decreased creating stresses and strains in the tissues. • The result is pain and dysfunction and can lead to serious injury.

  27. Principles of Body Mechanics • Alignment • Balance • Gravity • Friction

  28. Pathological Influences of Mobility • Postural Abnormalities • Impaired Muscle Development • Damage to CNS

  29. Systemic Changes Associated With Immobility • Metabolic changes: • Endocrine metabolism affected • (decrease in BMR) • Disrupts metabolic functioning • Fluid & electrolyte Imbalances • Decreased calories & protein • Negative Nitrogen Balance • Calcium Resorption affected • Functioning of GI tract

  30. Respiratory Changes • Lack of exercise & movement put client at risk for: • Atelectasis-Collapse of alveoli leading to partial collapse of lung • Hypostatic Pneumonia- Inflammation of lung tissue from stasis or pooling of secretions • Both decrease oxygenation, prolong recovery, & add to discomfort

  31. Cardiovascular Changes • Orthostatic hypotension • Increased workload of heart due to decrease in venous return to the heart • Risk for thrombus

  32. Musculoskeletal Changes • Muscle effects (muscle atrophy) • Skeletal effects- Disuse osteoporosis, contractures and foot drop

  33. Urinary Elimination Changes • pooling of urine in renal pelvis leads to increased risk for infection and renal calculi • Risk for dehydration and decreased urine output • UTI

  34. Nursing Process: Nursing Diagnosis • Health Promotion • Acute Care: • Metabolic system • Respiratory system • Cardiovascular system • Musculoskeletal system • Elimination system

  35. Metabolic System • Evaluate muscle atrophy • Assess wound healing • Assess edema • Assess for dehydration • Assess nutritional status (protein and vitamin supplements)

  36. Respiratory System • Frequent respiratory assessment • Ascultate lung sounds • Inspect chest wall movement • Promote lung expansion and stasis of pulmonary secrections • Deep breathing and coughing exercises • Incentive spirometer • Chest physiotherapy • Hydration • Positioning every 2 hours

  37. Cardiovascular System • Vital sign monitoring • Assess for orthostatic changes (Baseline BP) • Reduce workload of heart • Peripheral pulse assessment • Assessment of edema (hearts inability to handle increased work load) • Prevent thrombus formation

  38. Musculoskeletal System • Assessment of muscle tone, strength, loss of muscle mass, contractures • Assess for risk of disuse osteoporosis • Physical therapy consult • Prevent foot drop and contractures

  39. Tractionis the application of a pulling force to a part of the body

  40. Purpose: • to minimize muscle spasms; • to reduce, align, and immobilize fractures; • to reduce deformity; and • to increase space between opposing surfaces

  41. PRINCIPLES OF EFFECTIVE TRACTION • countertractionmust be used to achieve effective traction. Countertraction is the force acting the opposite direction. • Usually, the patient's body weight and bed position adjustments supply the needed countertraction.

  42. Types: • Straight or running traction • Balanced suspension traction

  43. Traction may be appliedto • the skin (skin traction) or directly to the bony skeleton (skeletal traction).

  44. Skin Traction: • Skin traction is used to control muscle spasms and to immobilize an area before surgery. • Skin traction is accomplished by using a weight to pull on traction tape or on a foam boot attached to the ­skin. The amount of weight applied must not exceed tolerance of the skin.

  45. Complication of skin traction: • Skin breakdown, • Nerve pressure • Circulatory impairment

  46. Nursing Intervention: • Ensuring Effective Traction: • Monitoring and Managing potential Complication

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