Chapter 1-Basic concept in physics-2022-2023- final.pptx
- 2. Basic Concept in Biomechanics 2 Ch.1 : Basic Concept in Physics File no. 1
- 3. Content Layout 1. Introduction (SI Units , prefixes, physics quantities types) 2. Translation Motion of objects 3. Force and Newton`s Law of motion 4. Work, energy, power 5. Rotational motion of objects, torques and lever system 6. Pressure and Hydrostatic pressure 3
- 25. Jehad Ahmed ALSHANTY 25 Q.3: Federal guidelines suggest that the maximum safe sideways acceleration in a turn is 1 𝒎 𝒔𝟐 . What is the minimum radius curve a civil engineer should design on a road where cars travel at 30 m/s ?
- 36. Inertia: the resistance an object has to a change in its state of motion. Mass: is a fundamental property of the object; a numerical measure of the amount of matter in the object. It is a quantitative measure of inertia Weight : is the force of gravity on an object. • Inertia • Mass • Weight Jehad Ahmed ALSHANTY 36 Inertia/mass/weight
- 37. Jehad Ahmed ALSHANTY 37 Mass Does not depend on gravity Always remains constant vs. Weight Depends on gravity W=m x g weight of an object changes if the gravity changes Mass vs Weight
- 38. Jehad Ahmed ALSHANTY 38 H.W.2:A bacterium, using its flagellum as propulsion, can move through liquids at a rate of 0.003 m/s. Its mass is 𝟏 × 𝟏𝟎−𝟏𝟐 g. The viscous drag on a swimming bacterium is so great, that if it stops beating its flagellum it will stop within a distance of 0.01 nm. a) What is the acceleration that stops the bacterium? b) What is average magnitude of this viscous force? c) What amount of force must the flagellum generate to push the bacterium at a constant velocity of 0.003 m/s d) If the bacterium wished to accelerate at a rate of 0.001 𝒎/𝒔𝟐 how much additional force would be necessary?
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- 44. • Work • Energy • Power
- 45. 45 Work and Conservation of Energy 1. Conservative force : A force is conservative when the work it does on a moving object is independent of the path between the object's initial and final positions. Examples: Electrical force, gravitational force, elastic force 2. Non-conservative force : A force is nonconservative when the work it does on a moving object is dependent of the path between the object's initial and final positions Examples: Friction, Applied Force, Tension Force
- 48. 48 Energy Conversion in Humans • Our own bodies, like all living organisms, are energy conversion machines. • Conservation of energy implies that the chemical energy stored in food is converted into work, thermal energy, and/or stored as chemical energy in fatty tissue. • The fraction going into each form depends both on how much we eat and on our level of physical activity. If we eat more than is needed to do work and stay warm, the remainder goes into body fat
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- 62. What the type of each lever class according to its mechanical advantage?
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- 67. • Pressure is an expression describe the magnitude of the force applied perpendicular to a unit area of the surface of an object over which that force is distributed. • It is a scalar quantity. • It represented by the symbol P . • Its SI unit is Pascal • There is a non-SI units for pressure like 67 Pressure 𝟏 𝑷𝒂𝒔𝒄𝒂𝒍 = 𝑵 𝒎𝟐
- 68. Jehad Ahmed ALSHANTY 68 Force/Pressure/Area The greater the area affected by the force the lower the pressure
- 69. Jehad Ahmed ALSHANTY 69 Pressure and State of Matter • A solid exerts pressure only in the downward direction due its weight • Liquids and gases exert pressure in all directions. Because its molecules move randomly and exert an equal force on every surface in contact with them.
- 70. • The pressure exerted by a non-moving (static) fluid at a given point within the fluid, due to the force of gravity is called the hydrostatic pressure. • The fluid pressure does not depend upon the shape of the container or the amount of liquid in the vessel. It depends on the depth and its density. Jehad Ahmed ALSHANTY 70 Fluid Pressure Video
- 71. • In the same fluid container, pressure increase as the fluid height increase. • Fluid exert equal pressure in all direction in the same depth. Jehad Ahmed ALSHANTY 71 Fluid Pressure • Static Fluid pressure given by the formula : m : mass V: Volume g : 10 m/s2 𝝆: 𝒅𝒆𝒏𝒔𝒊𝒕𝒚 ( 𝒌𝒈 𝒎𝟑 ) Wearing compression socks places pressure on the veins in the lower legs. This pressure can help improve blood flow and prevent further spider or varicose veins
- 72. Jehad Ahmed ALSHANTY 72 Absolute Pressure = total pressure Gauge pressure 𝑷𝒂𝒕𝒎= 𝑷𝒂𝒃𝒔= 𝒉 = 𝒎 𝒔𝟐 ≈ 𝟏𝟎 𝒎 𝒔𝟐 Atmospheric pressure
- 74. Jehad Ahmed ALSHANTY 74 H.W. 4: If the force on the eardrum increases by about 1.5 N above the force from atmospheric pressure, the membrane can be damaged. If you go for diving in the ocean, below what depth could damage to your eardrum start to occur? The eardrum is typically 8.2 mm in diameter and sea water density is 1030 𝒌𝒈 𝒎𝟑 Hydrostatic pressure 5
- 75. Sec.1.2: Review of Electricity Ch.1: Basic Concept in Physics 75
- 76. What is Electricity ? • Matter is made of very small particles called atom • Atom has a nucleus, which consist of protons and neutrons, and electrons located outside nucleus. • When electrons move from one atom to another atom, it produce electricity. • Electricity: is the energy caused by moving electrons from one place to another. Jehad Ahmed ALSHANTY
- 77. Electrical Charge • Electric charge is one of the property of matter that determine how the matter interact with each other. This interaction is done by mean of electrical forces. • Charge can be positive or negative, if there are excess of electrons in a particle they are said to be negatively charged. And if a particle has less number of electrons, they are called positively charged particles. • Charge is a conserved quantity, it cannot be destroyed or created • Its SI unit is Coulombs (C). • It represented by the symbol Q. • The charge of an electron is -1.6×10−19 C Jehad Ahmed ALSHANTY
- 78. Electrical Force • Charges exert forces on each other, based on the law of electric charges it could be attractive or repulsive forces. • The Electric force F between two charged bodies is proportional to the product of their charges Q1 and Q2 and is inversely proportional to the square of the distance R between them. This law is called Coulomb's Low , given as +1 -1 Jehad Ahmed ALSHANTY
- 79. • The electric field magnitude that is set by a charged particle is inversely proportional to the distance from the particle. • Force field E at any point is defined in terms of the electrostatic force F that would be exerted on a positive test charge q0 placed there. 79 Electrical Field • The electric field is radially outward from a positive charge and radially in toward a negative point charge.
- 80. Electrical Potential Difference • The electric potential difference, also known as voltage, is the external work done to push a unit positive charge from a reference point to a specific point against an electric field. • If the particle moves against the electric field it gains some amount of energy which is defined as the electric potential energy: Energy =∆VQ 𝑽𝒐𝒍𝒕 = 𝑱𝒐𝒖𝒍𝒆 𝑪𝒐𝒖𝒍𝒐𝒎𝒃
- 81. • The capacitor is an electrical component that stores electric charges in electronic circuits • Its consist of two conducting materials, separated by a gap containing a non-conducting material like air. • If the capacitor is fully filled and in the absence of any source power in the circuit, it can work as a battery • Capacitance of a capacitor is constant and measured in Farads (F). 81 Capacitor It’s the constant ∆𝑽 𝑬 = 𝟏 𝟐 𝑪 𝑽𝟐
- 82. DC Shock Defibrillator Jehad Ahmed ALSHANTY 82 • In this method a capacitor is charged to a high DC voltage and then rapidly discharged. • The amount of energy discharged by the capacitor may range between 2-400 Joule with peak value of current 20 A Extra • A corrective shock of 750-800 volts is applied within a tenth of a second to convert an abnormal heart rhythm to a normal heart rhythm as in the case of atrial fibrillation.
- 83. Current • The movement of charges due to potential difference establish an electric current. • It could be a DC or AC type. • It represented by the symbol I and given by: Its SI-unit is amperes (A) = (C/s) Where Q is the amount of charge travel through a conductor with a given cross-section area in a given time Jehad Ahmed ALSHANTY
- 84. Resistance • Electrons can flow through any material, but does so more easily in some material than in others. How hardly it flows is called resistance. • Matter can be broken down into: V = R I 1. Conductors: electrons flow easily Low resistance. 2. Semi-conductors: Variable resistance according to formulation and circuit conditions. 3. Insulator: electrons flow with great difficulty High resistance. • The resistance of a material (R) is measured in Ohms (Ω) • A resistor is the electrical component that implements electrical resistance in electronic circuits. It used to reduce current flow. • Ohm’s law : It’s the constant Jehad Ahmed ALSHANTY
- 85. 85 Electricity and Magnetism • An Electric Field surrounds any electric charge. • Moving electric charge creates Magnetic Field 𝑩 in its surrounding area. • A magnetic field exists in the region around a magnet. • The unit of B (in SI unit) is Tesla. While the magnetic field lines produced by a current flow on a long straight wire form concrete circles around the wire, where the magnetic field always at a direction perpendicular to the current flow. The magnetic field is a vector quantity. Outside the magnet, it points from the north pole to the south pole.
- 86. 86 Induced Current • The current that is produced in the wire in this case is called the induced current and its flows in the direction so that to opposeيعاكس the change in the flux. It creates an induced magnetic filed also. • When a magnet is moved near a conducting wire, current flows through that wire without any batteries! As this motion change the magnetic field through the wire area and hence the magnetic flux changing.
- 87. 87 Flux of Magnetic Field • Magnetic flux is the amount of magnetic field that passes through a loop • Magnetic flux is a scalar. The unit of magnetic flux (in SI) unit is the weber (1Wb=1 T.𝑚2)