Physics SA2 Overall Revision Notes

Pure Physics SA2 Overall Revision Notes General Physics: Chapter 1 Measurement Physical Quantities Derived quantities (combining suitable base quantities) E.g. Velocity Base quantity Name of SI unit Symbol Measurement of Length Very short Micrometer 0.01mm Length Metre M (diameter of small Screw (0.001cm) Mass Kilogram Kg wire) Gauge Time Second S Short (diameter of Vernier 0.01cm Electric current Ampere A coin) Calipers Thermodynamic Kelvin K Medium (Length of Metre Rule 0.1cm temperature pendulum) Luminous intensity Candela Cd Long (Length of Measuring 1cm Amount of substance Mole mol vehicles) tape Vernier Calipers: Total the values of the main scale and vernier scale readings to obtain the correct reading. Remember to take note of zero error. Micrometer Screw Gauge: Total the values of the main scale (1mm) and circular scale readings (0.01mm) to obtain the correct reading. Take note of zero error. Measurement of Time: Time can be measured with a pendulum, clock or stopwatch. 1.) The time taken for 1 complete oscillation is called the period. 2.) The number of complete oscillations per second is called the frequency. 3.) The period increases with the length of the pendulum. esto N nois iRev l eralv O 2SA s csiyh Pre u P 900 21 Pure Physics SA2 Overall Revision Notes General Physics: Chapter 2 Kinematics Types of Quantities Scalar Quantities are fully described by a magnitude only. Distance (m) Vector Quantities are quantities described by a magnitude and direction. Displacement: The distance measured along a straight line in a stated direction with respect to the original point (vector). Velocity: Rate of change of displacement Displacement (m)Velocity  Time Taken (m/s) Acceleration: Rate of change of velocity Final Velocity  Initial VelocityAcceleration  Note: Negative Acceleration = Retardation Time Taken (m/s) Displacement – Time Graphs (xt Graphs) Velocity – Time Graphs (vt Graphs) 3.) Used to show displacement over time. 1.) Used to show velocity over time. 4.) Horizontal line: Body at rest. 2.) Such a graph can be used to find: 5.) Straight line with positive gradient: Uniform a. Velocity Velocity. b. Acceleration: Gradient 6.) Straight line with negative gradient: Uniform c. Distance travelled: Area under the velocity in the opposite direction. graph. 7.) Curve: Non – uniform velocity. 8.) The gradient of the tangent of this graph gives the instantaneous velocity of the object. Accele ration of Free – Fall 2. Th e acceleration of free-fall near the surface of the Earth is constant and is approximately 10m/s2. It is derived from the gravitational force felt by objects near the Earth surface and independent of the mass of any object. 3. Speed of a free-falling body (experiencing no other forces other than gravity) increases by 10m/s every second or when the body is thrown up, it decreases by 10m/s every second. est4. The higher the speed of an object, the greater the air resistance. o N noi5. Terminal Velocity: When an object is moving at constant velocity, acceleration is 0. si Rev 6. As an object falls, it picks up speed, increasing air resistance. Eventually, air resistance becomes large enough l to balance the force of gravity where the acceleration of the object is 0, reaching constant velocity. eralvO 2SAs csiyh Pre uP 9002 2 Pure Physics SA2 Overall Revision Notes General Physics: Chapter 3 Forces Balanced / Unbalanced Forces Force SI unit: Newton (N) Is a push or a pull. When forces are balanced, there is no resultant force, thus no change wil occur to the object Effects of Forces Newton’s 3 When forces are unbalanced, on Motion Law of Motionthere is a resultant force, thus object wil move towards the direction with greater force Law of InertiaF = maEvery action has an equal and opposite reaction How reluctant an object Resultant Force acting Forces always occur in is to change. The greater on an object = Product pairs the mass the more of mass and acceleration Action / reaction forces reluctant it is. of object. act on different bodies. An object at rest will remain at rest and an object at motion will Friction remain at a constant speed with an absence of 1. It is the net force that slows down moving objects. a resultant force. 2. Acts in the opposite direction of motion of object. Static Friction: Related Factors affecting the amount Advantages: Walking / Brakes / to objects which are not of friction: object to remain slanted moving. Amount of force applied = amount of 1. Material / texture in Disadvantages: Reduction in friction. contact efficiency of machinery / energy Moving Friction: Applied 2. Proportional to force wasted as heat. force does not affect pressing surface friction. It can be 3. Independent on area of Methods to reduce friction: affected by surface / contact. Lubricants, ball / roller bearings, sudden mass change moving parts made smoother. est oNTerminal Velocity no i1. The greater the velocity of an object, the higher the air resistance. si2. Definition: The constant maximum velocity reached by a body falling through the atmosphere under the Rev attraction of gravity. l3. When an object reaches terminal velocity, the force of gravity and air resistance are balanced, the object falls eral vat a constant speed and doesn’t accelerate. O 24. Factors affected: Size, surface area, weight and nature of medium where object is flying. SA5. NOTE: If an object is falling through a vacuum, there would be no air resistance, thus acceleration is due to s cgravity alone. si yhPre uP 90 023 Pure Physics SA2 Overall Revision Notes General Physics: Chapter 4 Mass, Weight, Density Mass Weight Density Definition Mass is the quantity of matter Weight is the attractive force exerted Density of a substance is defined as its contained in an object. on an object due to gravity. mass per unit volume. SI unit Kilogram (kg) Newton (N) kg/m3 or g/cm3 Equation W  mg W: Weight of object (N) m: Mass of object (kg) g: Gravitational Acceleration in m/s2 Pure Physics SA2 Overall Revision Notes General Physics: Chapter 5 Turning Effects of Forces (Moments) Chapter 5.1: Definitions 1. The moment of a force is the turning effect of a force, or the ability of the force to make something turn. 2. Moment of a force (M) about a point O is the product of the force (F) and the perpendicular distance (D) from the point to the line of action of the force. 3. SI unit: Newton (N) 4. Moments can be clockwise or anticlockwise. 5. The turning effect of a force depends on: a. Location of applied force b. Perpendicular distance between the point of application of the force and the pivot. estoN no isi RevChapter 5.2: Principle of Moments lThe principle of moments state that: eralvO When a body is in equilibrium, the sum of clockwise 2SAmoments about the balanced point is equal to the sum s cof anticlockwise moments about the same point siyh (pivot). Pre u Total clockwise moment = Total anticlockwise moment. P 906. When the clockwise moment is not equal to the 02anticlockwise moment, there is a resultant moment. The 4 object will rotate in the direction of resultant moment. 7. Therefore, if there is no resultant moment, the object is balanced! Chapter 5.3: Centre of Gravity (c.g.) 8. Definition: The centre of gravity (CG) of a body is an imaginary point where the whole weight of the body seems to act in any orientation. a. The CG of a regular object is at the centre. b. The CG of an irregular object is determined using a plumb line. 9. If a body is hanging freely at rest, its centre of gravity is always vertically below the pivot, thus the plumb line method works. It can only be used for flat, irregular objects. Chapter 5.4: Stability 10. Stability is a measure of the body’s ability to maintain its original position. 11. There are 3 types of stability: Stability Type Effect Explanation Stable Object will return into Weight will generate an anticlockwise moment by bringing the cone back to Equilibrium original position after slight its original position (done by the restoring moment). disturbance These types of objects usually have low CG and big/heavier bases. Unstable Object will topple/fall after The weight of the cone will generate a clockwise moment outside the base Equilibrium slight disturbance area of the cone, thus there is a resultant moment and the object will fall. Neutral Object remains in new The centre of gravity neither rises nor falls, it remains at the same level. The Equilibrium position after slight lines of action of the 2 forces always concide and there is no moment disturbance provided by weight to turn the cone. 12. Ways to improve stability of an object: a. Lowering the CG (A lower CG will allow the line of action to act within the base area of an object) b. Area of its base should be as wide as possible (allow line of action to act within base area) estoN noisiRev l eralvO 2SA s c siyh Pre uP 900 25 Pure Physics SA2 Overall Revision Notes General Physics: Chapter 6 Energy, Work, Power Work Energy Power Definition Work done on an object is when Energy is the capacity to do work. Power is defined as the rate of doing a constant force is applied on There are many different types of work (Rate of energy transfer / the object producing a distance energy like translational, rotational and conversion) moving in the direction of the vibrational kinetic energy. force. SI unit Joule (J) Joule (J) Watt (W) Definition One joule of work is done when One joule of work is done when an One watt is produced when 1 joule of of SI unit a force of one Newton moves object with 1kg moves at 1m/s. work is done for 1 second. through a distance of one metre in the direction of the force. Equation W  FS 1W or E2K.E.: mvP W: Work done by constant force 2t(J) K.E: Kinetic Energy, m = mass (kg) P: Power (W) F: Constant Force (Newton) v = velocity (m/s) W: Work done (J) S: Displacement of force .P E.: mgh E: Energy (J) m = mass (kg), g = Gravity Field t: Time taken (seconds) Strength, h = height of object (m) Other Info. Work is done on an object only The principle of conservation of energy Efficiency when the force applied on it states that energy cannot be created or Useful energy output produces motion. destroyed, but can only change from = 100%one form to another. Total energy input Pure Physics SA2 Overall Revision Notes General Physics: Chapter 7 Pressure Pressure in a solid Pressure in a liquid Pressure in a gas Definition Pressure is the force acting normal or perpendicularly per unit area. SI unit Pascal (Pa) or N/m2 Equation ForcePressure = hgThe air surrounding us exerts a Pressure = Areah: Depth of the liquid (m) pressure in all directions which is p: Density of liquid (kg/m3) about 105 Pa. g: Gravitational field strength Other Info. This formula can only 1. A liquid exerts pressure because of 1. A barometer is used to measure estobe used for solids. its weight. pressure. It consists of an inverted N n2. Liquid pressure acts equally in all tube in a dish of mercury. The oisdirections. This is because particles space above the mercury in the iof the water can flow and wrap tube is vacuum. Rev laround the object. 2. Liquid mercury is used as its eralHydraulics Systems density is very high and a shorter vO Purpose: Increase the output force barometer can be used to show 2from an input force. However the atmospheric pressure. SAs height which the object can be 3. An object can be bent/sucked in csiincreased is reduced. due to the production of vacuum yhP Properties used: Liquids are and due to the difference in re incompressible and if pressure is pressure; the atmospheric uP applied to trapped liquid, it is pressure will press on the object. 90transmitted to all parts of the liquid. 02 6 Pure Physics SA2 Overall Revision Notes Thermal Physics: Chapter 8 Temperature Temperature It is a measure of the degree of hotness of a body. Physical Properties : 1. Expansion of column of liquid Measured using a thermometer in capillary tube Temperature Scale 2. Voltage of thermocouple 3. Expansion of a bimetallic strip The Celsius Scale The Kelvin Scale Desirable Features Ice Point: Temperature of pure melting ice at Zero: Absolute Zero (where object 1. Easy to read scale standard atmospheric pressure (0oC). has nothing in the body) 2. Safe Steam Point: Temperature where boiling Unit: Kelvin (K). 3. Sensitive to temperature water changes to steam at standard  K( C) 273K changes atmospheric pressure. 1oC increase = 1 K increase. 4. Wide range of temperature General Equation Types of Thermometers Measured Physical Property   Total Range of Physical PropertyClinical Thermometer, Liquid in Glass Thermometer, Thermocouple Difference between Mercury / Alcohol Thermocouple thermometer 1. Consists of 2 wires of different materials Mercury Alcohol joined together to form 2 junctions. Uniform Yes No (Out of 2. A voltage is produced when the junctions are Expansion Range) at different temperatures. It increases as the Stick to Glass No (visible Yes temperature increases. meniscus) (Transparent) 3. Suitable for measuring wide temperature Reaction to Quick Slow differences, which vary rapidly due to its temp. changes quick response and temperature at a point as Range Measure Measure lower wire junctions are small. Higher Temp. temp. 4. Can be connected in series to increase Cost Expensive Cheap sensitivity. Poisonous Yes No esto N noi siRev l eralv O 2SA s csiy hPre u P 900 27 Pure Physics SA2 Overall Revision Notes Thermal Physics: Chapter 9 Kinetic Model of Matter The kinetic theory of matter states that all matter is made up of large number of tiny atoms or molecules which are in continuous motion. Molecular Model of the 3 states of matter Solid Liquid Gas Forces between Molecules Balanced, strong As strong as solid Negligible Distance between Small, arranged in regular Slightly further apart, no Far apart, mainly empty molecules pattern pattern space Motion of molecules Vibrate about fixed Vibrate to and fro Move randomly with high positions speed, colliding with one another and walls. Compression No No Yes When heated Molecules gain energy Molecules vibrate and Move at higher speed, and vibrate more, move about more collision with one another separation between vigorously, separation and walls increases. molecules increase between molecules Expands the most. slightly increase slightly Diffusion Pressure exerted by a gas It is the spreading of molecules on their own When a gas molecule hit the walls of the container, it accord without any external aid. exerts a force on the container. Occurs in liquids and gases Pressure increases when: Occurs as particles are in random motion 1. Volume of container decreases at constant Depends on temperature and density temperature (concentration) of fluid. The lower the 2. Temperature of gas increases at constant volume density, the more space for particles to 3. Number of gas molecules increase, total pressure move into. exerted increases. esto N nois iRev l eralv O 2SA s csiyh Pre u P 900 28 Pure Physics SA2 Overall Revision Notes Thermal Physics: Chapter 10 Transfer of Thermal Energy Transfer of Thermal Energy: When 2 objects are placed in contact with one another, their temperature eventual y becomes the same, known as thermal equilibrium. Note: Heat travels from a region of high temperature to low temperature.ConductionConvectionRadiationHeat is transmitted layer by Process where heat is A method of heat transfer layer through a medium from transmitted from one wher ethe source of heat one particle to another.place to another by the movement of heated transmit energy through particles of a gas/liquid.electromagnetic waves. A medium is not required.Collision Flow of free between electrons Mechanism: neighbouring (conductors Change in Factors: Temperature of object, particlesonly)Density. surface of object, surface area of object. Good emitters are also good absorbers of radiation. Conduction: 1. Collisions between neighbouring particles. a. Particles nearer to heat source gain energy and vibrate faster. b. Particles collide into less energetic neighbouring particles which gains kinetic energy. c. The less energetic particles vibrate faster, collides into other particles. d. Process continues layer by layer to spread the heat to cooler parts. 2. Flow of free electrons (conductors only) a. Electrons near heat source gain energy, move faster. b. Free electrons can move between the particles and collide with other electrons, allowing the less esto energetic electrons to gain energy and move faster. N nc. Process continues to spread the heat to cooler parts. oisi RevConvection l 3. Fluid nearer to heat source gains heat and expands. eralv4. Expansion causes decrease in density for the fluid nearer to heat source, causing it to rise. O 5. The hotter fluid rises over the cooler fluid while the cooler fluid rushes in to take the space. 2SA6. The process continues and a convection current is formed. s c7. Convection is faster than conduction as there is bulk movement (all the molecules get hot and move up, siythus it is faster than conduction. h P re u P 9002 9 Pure Physics SA2 Overall Revision Notes Light, Waves and Sound: Chapter 12 Light Speed: 3 x 108 Path it tr avels is a light ray. Can be parallel beam, converging beam or diverging beam. Light Objects which give out light are luminous objects, those which doesn’t are non-luminous. Chapter 12.1: Reflection of light Important terms: Incident Ray: Light ray hitting the reflecting surface. Reflected Ray: Light ray reflected from the reflecting surface. Normal: The perpendicular to the reflecting surface at the point of incidence. Angle of incidence (i): The angle between the incident ray and the normal. Angle of reflection (r): The angle between the reflected ray and the normal. Laws of Reflection: The incident ray, reflected ray and the normal of the reflecting surface lie on the same plane. Angle of incidence = Angle of Reflection Regular Reflection Diffuse Reflection Occurs at smooth surfaces. Occurs at rough surfaces (sandpaper, burnt Parallel light rays incident boots). Parallel light rays incident on the on the surface are reflected surface is reflected in all directions. The in one direction only (all rays normals are not parallel. have the same incident/ reflected ray). The normals of all points of incidence are equal. estoCharacteristics of image formed by plane mirror N n Same size as object ois Laterally inverted i Upright Rev l Virtual (not real, cannot be captured on screen) eralThe distance of the image from the mirror = distance of vOobject from the mirror. 2 SAApplications of Mirrors: s c si Optical Testing (Mirrors can make letters appear further y haway, saving space) P Blind Corners (for drivers) re u Periscopes P 90 02 10