General Physics 1 Reviewer PDF

GENERAL PHYSICS 1 SECOND QUARTER REVIEWER I. MOMENTUM ROTATIONAL MOTION  also known as Angular Motion or Circular Motion  refers to the motion of objects in a circular...

GENERAL PHYSICS 1 SECOND QUARTER REVIEWER I. MOMENTUM ROTATIONAL MOTION  also known as Angular Motion or Circular Motion  refers to the motion of objects in a circular path UNIFORM CIRCULAR MOTION  refers to motion of objects under uniform circular speed ANGULAR DISPLACEMENT The symbol generally used for angular displacement is θ (theta). θ is the angle swept by the radius of a circle that points to a rotating object. Angular displacement is unitless since it is the ratio of two distances but, we will say that the angular displacement is measured in radians. Note: 1 complete revolution = 360⁰ = 2𝜋 𝑟𝑎𝑑𝑖𝑎𝑛𝑠 = 6.28 rad Angular velocity In rotational motion, angular velocity (ω) is defined as the change in angular displacement (θ) per unit of time (t). Angular velocity is described as revolution per second (rev/sec, rps) radian per second. Angular acceleration, α It is the change in the angular velocity, divided by the change in time. The angular acceleration is a vector that points in a direction along the rotation axis. The unit of angular acceleration is radians/𝒔𝟐. All points in the object have the same angular acceleration. Every point on a rotating has, at any instant a linear velocity (v) and a linear acceleration (a) Conventionally, object moving counterclockwise has a value of positive (+) angular acceleration, while the one moving the clockwise direction has negative (-) value. ROTATIONAL DYNAMICS Torque  is a physical quantity closely related to rotation. It is the Force’s ability to cause an object to rotate.  also called the Moment of Force, is the result of the force that can cause an object to rotate about an axis. It is a vector quantity. It is the cross product of the vector Force and the distance from the axis of rotation. The symbol used for torque is the Greek letter tau (τ)  Torque is the product of force (F) and the lever arm (I) The direction of the torque may either be counterclockwise (CCW) or clockwise (CW). By convention, we take the counterclockwise direction to be positive and clockwise as negative. STATIC EQUILIBRIUM  Static equilibrium occurs when an object is at rest – neither rotating nor translating. ANGULAR MOMENTUM  is a quantity that tells us how hard it is to change the rotational motion of a particular spinning body. For a single particle with known momentum. II. GRAVITY GRAVITATIONAL FORCE The example of gravitational attraction that’s probably most familiar to you is your weight, the force that attracts you toward the earth. During his study of the motions of the planets and of the moon, Newton discovered the fundamental character of the gravitational attraction between two any bodies. Along with his three laws of motion, Newton published the Law of Gravitation in 1687. It may be stated as follows: The presently accepted value of G is G = 6.67428 (67) x 𝟏𝟎−𝟏𝟏 N 𝒎𝟐 / 𝒌𝒈𝟐 To three significant figures, G = 6.67 𝟏𝟎−𝟏𝟏 N 𝒎𝟐 / 𝒌𝒈𝟐 Because 1 N = 1 kg m/𝑠2 , the units of G can also be expressed as 𝒎𝟑 / kg 𝒔𝟐.) ORBITS The only force acting on a satellite in circular orbit around the earth is the earth’s gravitational attraction, which is directed toward the center of the earth and hence toward the center of the orbit. This means that the satellite is in uniform circular motion and its speed is constant. The satellite isn’t falling toward the earth; rather, it’s constantly falling around the earth. In a circular orbit, the speed is just right to keep the distance from the satellite to the center of the earth constant. KEPLER’S LAW OF PLANETARY MOTION The name planet comes from a Greek word planetes meaning “wanderer,” and indeed the planets continuously change their positions in the sky relative to the background of stars. One of the great intellectual accomplishments of the 16th and 17th centuries was the threefold realization that: 1. The earth is also a planet 2. all planets orbit the sun, 3. the apparent motions of the planets as seen from the earth can be used to precisely determine their orbits LAW OF ORBITS The first law explains that all planets move in elliptical orbits with the sun at one focus. An ellipse is a shape that resembles a flattened circle. How much the circle is flattened is expressed by its eccentricity. The eccentricity is a number between 0 and 1. It is zero for a perfect circle. LAW OF AREAS The second law describes a line that connects a planet to the sun and sweeps out equal areas in equal times. When a planet is near the sun, it travels faster and sweeps through a longer path in a given time. It follows from Kepler’s second law that Earth moves the fastest when it is closest to the Sun. This happens in early January, when Earth is about 147 million km (91 million miles) from the Sun. When Earth is closest to the Sun, it is traveling at a speed of 30.3 kilometers (18.8 miles) per second. LAW OF PERIODS The third law mathematically expressed as the square of the period of any planet is proportional to the cube of the semi- major axis of its orbit. III. MECHANICAL WAVES Oscillation or Vibration - “wiggle” in time An object initially set into vibration will have its amplitude continuously decreasing due to frictional effects. Eventually, the object will stop vibrating. This type of motion is called damped harmonic oscillation. Underdamped Oscillation - The system oscillates with decreasing amplitude until it becomes zero. Critically and Overdamped Oscillation - The system return to equilibrium without oscillating. A critically damped system returns to equilibrium faster than an overdamped system. Wave - “wiggle” in both space and time MECHANICAL WAVES - A kind of wave that requires medium to propagate. ELECTROMAGNETIC WAVE - Does not require a medium to propagate TYPES OF MECHANICAL WAVES 1. TRANSVERSE WAVES The direction of the motion of particles is perpendicular to the direction of the propagation of the wave. Crest – the highest point in transverse wave Trough – the lowest point in transverse wave Amplitude – the distance from the equilibrium line to the crest or trough Equilibrium Line – the stable position of a medium when it is in equilibrium 2. LONGITUDINAL WAVES The direction of the motion of particles and the direction of the propagation of the waves are in the same line. Compression– the region of high particle density. For fluids, this corresponds to a region of high pressure. Expansion or Rarefaction– the region of low particle density. For fluids, this corresponds to a region of low pressure. 3. BOTH TRANSVERSE AND LONGITUDINAL WAVES In some cases, the displacements of the particles have both transverse and longitudinal components. These are also called Rayleigh surface waves PERIODIC MOTION -refers to the motion that repeats itself regularly or at equal time intervals The number of complete revolutions or cycles of the ball around the circle per unit of time is called the frequency, denoted by small letter f. The unit of frequency is the number of cycles, revolutions or vibrations per second. The SI unit is hertz (Hz) SIMPLE HARMONIC MOTION -an oscillation that happens when the associated restoring force is directly proportional to the displacement from the equilibrium position HOOKE’S LAW “For every small deformation of an object, the displacement is directly proportional to the deforming force or load” SOUND WAVES -is a longitudinal wave. All creatures have distinct ranges of detectable sound frequency which are called the audible ranges. Sound frequencies that are above 20kHz are called ultrasonic and frequencies below this range are called infrasonic. PITCH - figures out how high or low we perceive the sound with the ear in an auditory way. As the frequency of sound increases, the pitch rises. The frequency of a wave is an object quantity that can be measured, while pitch refers to how different frequencies are perceived by the human ear. LOUDNESS - is directly related to the pressure amplitude. This means that for a given frequency of sound, a louder sound is perceived with greater pressure amplitude. TIMBRE OR TONE COLOR - Refers to the difference in sound. The timbre helps the listeners to identify which objects are the ones that produce a particular sound. DOPPLER EFFECT - Change in the frequency of sound. It was named after the Austrian physicist Christian Doppler (1803-1853) who first described it. IV. FLUID MECHANICS DENSITY AND PRESSURE Liquids and Gases are collectively known as Fluids. The field in Physics that studies the motion and the properties of fluids is called Fluid Mechanics. Density is an intensive property of a material. The SI unit of density is kg/𝒎𝟑. The specific gravity (SG) of a substance is defined as the ratio of the density of the substance and the density of water at 4⁰C. Because the specific gravity of water (at 4⁰C) is 1.00g/𝒄𝒎𝟑 = 1000kg/𝒎𝟑 , the specific gravity of a substance is numerically equal to its density specified in a unit of g/𝑐𝑚3. The pressure of fluids has a uniform density p that varies with depth. Note the greater the depth of the fluid is, the greater the pressure will be. Density is a measure of how close the particles are together. In liquids the density is uniform throughout and because there is so little space between the particles the density only slightly decreases with increase in temperature and with the increased kinetic energy of the particles. However, the volume shows almost no change with increased pressure. All liquids expand on heating. The pressure in a fluid varies and increases with depth – it doesn't matter whether you are dealing with gases like the atmosphere or liquids like the water of a lake or ocean. The greater the height/depth of fluid, the greater the weight of particles that gravity is pulling down, hence the increase in force per unit area at a particular level, hence the increase in pressure. PASCAL’S PRINCIPLE Pressure is defined as a measure of force over a given area. Pascal's law states that a pressure applied to a fluid in a closed container is transmitted equally to every point of the fluid 𝐹 and the walls of the container, as seen in Equation p = 𝐴 This pressure is transmitted equally in all directions and at right angles, and a change in pressure disperses equally throughout the fluid. Pascal's law is used by engineers when designing hydraulic systems that use liquid power to do work. Conversion of pressure = newton per square meter is pascal force per unit area psi = pounds per square inch The SI unit of the pressure is the Pascal with the formula sign Pa. 1 Pascal is equal to the pressure of 1 newton per square meter. 1 Pa = 1 N / m2 ≡ 1 kg / m · s2. ARCHIMEDES’ PRINCIPLE Archimedes' principle, named after an inventor and a mathematician who lived in ancient Greece, states that the buoyant force on a submerged object is equal to the weight of the fluid that is displaced by the object. Buoyancy is the ability of an object to float in water or air. The Archimedes principle states that the upward buoyancy force exerted on a body partially or completely immersed in a fluid is equal to the weight of the fluid that the body displaces and acts in an upward direction in the center of the mass of the displaced fluid. BERNOULLI’S PRINCIPLE Bernoulli’s Equation applies to a fluid flowing through a full pipe. The degree to which Bernoulli’s Equation is accurate depends on the degree to which the following conditions are met: 1. The fluid must be experiencing steady state flow. 2. The fluid must be experiencing streamline flow. 3. The fluid must be non-viscous. Bernoulli's principle is an idea of fluid dynamics. It says that as speed of the fluid increases, pressure decreases.... A higher pressure pushes (accelerates) fluid toward lower pressure. So any change in a fluid's speed must be matched by a change in pressure (force). V. TEMPERATURE AND HEAT Temperature -usually associated with the hotness or the coldness of an object. The field of science concerned with describing heat and its relationship with energy is called thermodynamics. The word thermodynamics comes from the Greek words therme, meaning “heat” and dynamicos meaning “movement”. ZEROTH LAW OF THERMODYNAMICS When two objects at different initial temperature reaches the same temperature at some point they are now in thermal equilibrium. There are three common scales of measurement for temperature Celsius Scale, ⁰C Fahrenheit Scale, ⁰F Kelvin Scale, K The change in temperature is referred to as “C⁰” (Celsius degree) In the Celsius scale, the freezing point of water was chosen to be 0⁰C, whereas the boiling point was chosen at 100⁰C. Thus, there are 100 gradations (or intervals) between the freezing and the boiling points of water for the Celsius scale. In the Fahrenheit scale, the freezing and the boiling point of water are assigned to be 32⁰F and 212⁰F respectively. Thus, the distance between the freezing and the boiling points of water is divided into 180 equal intervals. THERMAL EXPANSION - occurs once an object is heated the molecules tends to get excited and move faster and take up more space that tends the materials to expand or contract. Most materials expand when heated and contract when cooled except ice. When water is cooled and freezes at 0 degree Celsius frozen water expands by 9% becoming less dense. LINEAR EXPANSION - the change in the length of a body due to a temperature change VOLUME EXPANSION - the volume of materials changes when temperature changes HEAT AND HEAT CAPACITY There are three mechanics of heat transfer 1. Conduction -mechanism of heat transfer that requires contact between two objects with difference in temperature. The conduction occurs from higher to lower temperature objects. 2. Convection -the transfer of heat by the movement of fluid (gases or liquids) from one region of space to another. 3. Radiation -the transfer of heat by electromagnetic waves, such as visible light, infrared and ultraviolet radiation, which can propagate in a vacuum at the speed of light. VI. LAWS OF THERMODYNAMICS The objects that deals with the mentioned variables is called a system, while everything outside the system is referred to as the surroundings. The object or body that separates the two is the wall. 1. Open system - a system that has the ability to exchange mass and energy with its surroundings 2. Closed system - a system that can exchange energy with its surroundings; however, it is unable to do so with its mass 3. Isolated system - a system that can neither exchange mass nor energy with its surroundings Reversible Process - one in which the system and its surroundings can be returned to their initial state before undergoing a process. Cycle - a series of processes that starts and ends at the same condition. FIRST LAW OF THERMODYNAMICS - Also known as the law of conservation of energy. When heat is added to a system, some of it remains in the system, increasing its internal energy, while the rest leaves the system as the system does work. Thermodynamics Process 1. Isothermal Process A constant temperature process 2. Isobaric Process A constant pressure process 3. Isochoric Process A constant volume process 4. Adiabatic Process A process where there is no heat transfer occurring between the system and its surroundings The first law of thermodynamics says that work can be converted into heat. SECOND LAW OF THERMODYNAMICS Limits the amount of work a heat engine can do for a certain amount of heat. 1. Kelvin-Planck statement: No heat engine can completely convert heat energy to work. In other words, there is no 100 percent efficient heat engine. 2. Clausius Statement: Heat flows naturally from hot to cold objects. 3. Entropy statement: When a reversible process occurs, the total entropy of the universe remains the same. When an irreversible process occurs, the total entropy of the universe increase. Equivalently, the entropy of an isolated system remains the same or increases. Heat Engines A device that converts thermal energy to mechanical energy. Internal combustion engine -Burns the fuel inside the engine External combustion engine -Burns the fuel outside the engine Human body is considered as a heat engine with food as the main source of energy. However, only 20 to 30% of this energy is converted to useful work.