Gravitational force Dr B Kalpana Natural phenomenon by
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 • Rate of change of velocity with respect to time in either magnitude or direction • Gravity is the most common accelerative force
FACTORS AFFECTING ACCELERATIVE FORCES • • • Intensity Duration Rate of onset Body area and site Impact direction
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. 5
Newton’s Laws of Motion • 1 st 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. • 2 nd Law – Force equals mass times acceleration. • 3 rd Law – For every action there is an equal and opposite reaction.
1 st 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.
Objects on earth, unlike the frictionless space the moon travels through, are under the influence of friction.
2 nd Law The net force of an object is equal to the product of its mass and acceleration, or F=ma.
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.
Newton’s Law of Universal Gravitation http: //scienceblogs. com/startswithabang/upload/2009/07/meet_our_second_moon/400 px-Newtons. Law. Of. Universal. Gravitation. svg. png
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. 12
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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 -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 14 -15
● As one changes the relationship of the body the C of G may even be located outside the body. Fig 14. 4 14 -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 14 -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!
Relationship Between Weight and Mass • Weight force of gravity on object – Force • Mass measure of inertia of object – Amount of matter present
Characteristics of Uniform Circular Motion • • Tangential (linear) Velocity Frequency Period Centripetal Acceleration
Density and Specific Gravity The density ρ of an object is its mass per unit volume: (10 -1) The SI unit for density is kg/m 3. Water at 4°C has a density of 1 g/cm 3 = 1000 kg/m 3. The specific gravity of a substance is the ratio of its density to that of water. © 2014 Pearson Education, Inc.
The force or forces needed to bend the normally straight path of a particle into a circular or curved path is called the CENTRIPETAL FORCE. It is a pull on the body and is directed toward the center of the circle. Force on car Force on passenger Tendency for passenger to go straight
Without a centripetal force, an object in motion continues along a straight-line path. Remember Newton’s 1 st Law? With a centripetal force, an object in motion will be accelerated and change its direction. What is the centripetal force?
3 Important Equations v = 2 pr/T Period (T) = time for 1 rev
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
Benefits of proper Body Mechanics Ø Conserve energy Ø Reduce stress and strain to muscles, joints, ligaments, and soft tissue Ø Promote effective, efficient respiratory and cardiopulmonary function Ø Promote and maintain proper body control and balance Ø Promote effective, efficient, and SAFE movements
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.
Principles of Body Mechanics • Alignment • Balance • Gravity • Friction
Pathological Influences of Mobility • Postural Abnormalities • Impaired Muscle Development • Damage to CNS
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
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
Cardiovascular Changes • Orthostatic hypotension • Increased workload of heart due to decrease in venous return to the heart • Risk for thrombus
Musculoskeletal Changes • Muscle effects (muscle atrophy) • Skeletal effects Disuse osteoporosis, contractures and foot drop
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
Nursing Process: Nursing Diagnosis • • Health Promotion Acute Care: Metabolic system Respiratory system Cardiovascular system Musculoskeletal system Elimination system
Metabolic System • Evaluate muscle atrophy • Assess wound healing • Assess edema • Assess for dehydration • Assess nutritional status (protein and vitamin supplements)
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
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
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
• Traction is the application of a pulling force to a part of the body
Purpose: • • to minimize muscle spasms; to reduce, align, and immobilize fractures; to reduce deformity; and to increase space between opposing surfaces
PRINCIPLES OF EFFECTIVE TRACTION • countertraction must 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.
Types: • Straight or running traction • Balanced suspension traction
Traction may be applied to • the skin (skin traction) or directly to the bony skeleton (skeletal traction).
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.
Complication of skin traction: • Skin breakdown, • Nerve pressure • Circulatory impairment
Nursing Intervention: • Ensuring Effective Traction: • Monitoring and Managing potential Complication
Nursing Process: The patient in Traction • Assessment: • evaluate the body part to be placed in traction and neurovascular status (ie, color, temperature, capillary refill, edema, pulses, ability to move, and sensation) and compare it to the unaffected extremity.
Potential complication: • • • Pressure ulcer Pneumonia Constipation Anorexia Urinary stasis and infection Venous stasis
Urinary volume • • • Normal = 600 -1550 ml Polyuria- >2000 ml Oliguria-<400 ml Anuria-complete cessation of urine(<200 ml) Nocturia-excretion of urine by a adult of >500 ml with a specific gravity of <1. 018 at night (characteristic of chronic glomerulonephritis)
Urinometer • Take 2/3 of urinometer container with urine • Allow the urinometer to float into the urine • Read the graduation at the lowest level of urinary meniscus • Correction of temperature & albumin is a must. • Urinometer is calibrated at 15 or 200 c So for every 3 oc increase/decrease add/subtract 0. 001 For 1 gm/dl of albumin add 0. 001
HYDROMETERS – Combination - Master valve - Water meter - Flow sensor – Available sizes 1½” to 8”: - 1½” and 2” are threaded - 3” to 8” are flanged – Accommodate flow ranges from 1. 8 gpm to 1500 GPM 3” Hydrometer 1 1/2” Hydrometer
HYDROMETER FEATURES – Double chamber valve for positive opening and closing – no springs required – 6” Hydrometer is single chamber – Adding pilot valves and solenoids enables remote and automatic operation – Hermetically sealed register – just one part touches water – Optional control functions - Manual Electric - Pressure reducing manual electric - Other configurations upon request
WHY USE A HYDROMETER SAVES SPACE – Combination master valve, water meter and flow sensor all in one unit – Does not require any upstream or downstream straight pipe for proper function. ACCURACY ACROSS A WIDE FLOW RANGE – Accuracy is ± 2% across the entire flow range—offset is = 0 WATER METER CANNOT LOOSE DATA – Standard with odometer register
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