Summary PHY101 ( 2 ) T / Hanadi Al Harbi

Transcription

1 الكمية Physical Quantity القانون Low التعريف Definition الوحدة SI Unit Linear Momentum P = mθ be equal to the mass of an object times its velocity. Kg. m/s vector quantity Stress F \ A the external force acting on an object per unit cross-sectional are Elastic modulus stress / strain the ratio of the stress to the resulting: strain. N/ m 2 or kg/m.sec2 N / m 2 Density ρ= m \ v amount of matter per unit volume or is the ratio of mass to volume. kg.m 3 Pressure P = F/A force per unit area. N / m 2 = Pa scalar quantity. intensity I = P A the power P per unit area A w/m 2 The speed of sound waves v = B ρ If the medium is a liquid or a gas and has a bulk modulus B and density ρ, the speed of sound waves in that medium is Km/s 1

2 - Elastic Properties of Solids : The types 1 -Young s modulus 2- Shear modulus 3- Bulk modulus measures which measures the resistance of a solid to a change in its length. which measures the resistance to motion of the planes within a solid parallel to each other which measures the resistance of solids or fluids to changes in their volume. For solid length. Solid Shape solids or fluids volume Low Definition Tensile stress: the ratio of the magnitude of the external force F to the cross-sectional area A. Tensile strain: in this case the ratio of the change in length ΔLto the original length Li. Shear stress: ratio of the tangential force to the area A of the face being sheared. Shear strain: ratio Δx/h, where Δx is the horizontal distance that the sheared face moves and h is the height of the object. Volume stress: ratio of magnitude of total force F exerted on a surface to the area A of the surface. P = F/A is called pressure. If it changes by an amount ΔP = ΔF/A, then the object will experience a volume change ΔV. Volume strain : is equal to the change in volume ΔV divided by the initial volume Vi. Unit N / m 2 N / m 2 N / m 2 2

3 -Fluid mechanics is : the study of how fluids moveand the forces on them. divided into: Fluid statics the study of fluids at rest. Fluid dynamics the study of fluids in motion -- The types of collision : 1 / Elastic collision 2 / Inelastic collision - Momentum of the system is conserved in all collisions, but kinetic energy of the system is conserved only in elastic collisions. - Conservation of momentum: Whenever two or more particles in an isolated system (frictionless, no loss of energy) interact, the total momentum of the system remains constant. (total linear momentum before = total linear momentum after) - The result of a stress is strai, which is a measure of the degree of deformation. 3

4 -Matter is normally classified as being in one of four states: solid, liquid, gas, and plasma. -All of liquids, gases, and plasma are fluids. - pressure of the fluid at a depth is given by: - The pressure in a fluid changes linearly with depth. - Pascal s princible: A change in the pressure applied to an enclosed liquid is transmitted undiminished to every point of the liquid and to the walls of the container. 4

5 - Law of Archimedes: The buoyant force is equal to the weight of the replaced liquid or gas. -Buoyant Force B : which is equal in magnitude to the weight of the fluid displaced by the object. -The Surface of Liquid : cohesive forces forces between like molecules such as the forces between water molecules adhesive forces forces between unlike molecules such as those exerted by glass on water -The drop takes spherical shape because of a property of liquid surfaces called surface tension. -Viscosity refers to the internal friction of a fluid. 5

6 -The viscosity force F is given as : F = η A v L -The equation of continuity for fluids states that: The product of the area and the fluid speed at all points along a pipe is constant for an incompressible fluid (A 1 V 1 = A 2 V 2 = const) -The Bernoulli s equation is : (P ρv 2 + ρ g h = constant) 6

7 -Torricelli's law, also known as Torricelli's theorem, is relating the speed of fluid flowing out of an opening to the height of fluid above the opening. (P = P 0, and v 1 = 2 gh ) - Simple harmonic motion is : a special case of oscillatory motion that occurs when the restoring force is proportional to the displacement. -The spring force is : ( F = -kx) is called (Hooke s law) - Simple harmonic motion Components : 1- Position (x) : x = A cos ( ωt + ) 2- AMPLITUDE ( A ) : The maximum value of the position of the particle in either the (+x) or ( x) direction. 3- PHASE CONSTANT ( ): is determined uniquely by the position and velocity of the particle. 4- PERIOD ( T ): is the time interval required for the particle to go throughone full cycle of its motion. (T= 2π ) ω (ω = K m, has units of rad/s.). 5- FREQUENCY( f ): the number of oscillations that the particle undergoes per unit time interval,the units of f are cycles per second, or hertz (Hz). ( f= 1 T = ω 2π ) 7

8 -The simple pendulum: 1- angular frequency : ω = g l 2- PERIOD: 2π ω = 2π l g The period and frequency of a simple pendulum depend only on the length of the string and the acceleration due to gravity. -Wave: is a periodic disturbance traveling through a medium. All waves carry energy. Types of Waves: 1-Transverse wave A traveling wave or pulse that causes the elements of the disturbed medium to move perpendicular to the direction of propagation. an example: Water waves 2- Longitudinal wave A traveling wave or pulse that causes the elements of the medium to move parallel to the direction of propagation an example: Sound waves 8

9 - Sound Waves: are divided into three categories that cover different frequency ranges: (1) Audible waves :lie within the range of sensitivity of the human ear. (2) Infrasonic waves: have frequencies below the audible range. (3) Ultrasonic waves :have frequencies above the audible range. 9

10 They travel through any material medium with a speed that depends on the properties of the medium. -The speed of sound waves depends on: 1- the compressibility ( 1\B) 2- density of the medium ( ρ) 3-bulk modulus B if the medium is gas or liquid 4-the temperature of the medium. -Superposition principle: If two or more traveling waves are moving through a medium, the resultant value of the wave function at any point is the algebraic sum of the values of the wave functions of the individual waves. -interference of wave: One consequence of thattwo traveling waves can pass through each other without being destroyed or even altered -A standing wave : is an oscillation pattern with a stationary outline that results from the superposition of two identical waves traveling in opposite directions. -INTERFERENCE OF WAVES: 1/ constructive interference 2/destructive interference 10

11 -The Doppler Effect : General Case: 11