Physics 6091 Power Bank version 2.0

‘O’ Level Physics Power Bank! Version 2.0

Definitions in Physics 6091 O‐Level Syllabus Topics Definition Measurements A physical quantity is one that can be measured and consists of a numerical magnitude and a unit. Each complete to-and-fro motion of an object is one oscillation. The Period T of a pendulum is the time taken for a complete oscillation. Kinematics Scalar quantities are physical quantities that have magnitude only. Vector quantities are physical quantities that possess both magnitude and direction. Speed is the distance moved per unit time. Displacement is distance travelled in a specified direction. Average speed is total distance travelled over total time. Velocity is the rate of change of displacement. Acceleration is the rate of change of velocity. Uniform Acceleration is the constant rate of change of velocity. Free fall is when an object falls and experiences only the gravitational force. Dynamics A force is a push or a pull that one object exerts on another. Newton’s 1st Law of motion states that every object will continue in its state of rest or uniform motion in a straight line unless a resultant force acts on it. {note : This is also known as Law of Inertia} Newton’s 2nd Law of motion states that when a resultant force acts on an object of constant mass, the object will accelerate and move in the direction of the resultant force. The product of the mass and acceleration of the object is equal to the resultant force. One Newton (1 N) is defined as the force that will produce an acceleration of 1 m s-2 on a mass of 1 kg. Newton’s 3rd Law of Motion states that for every action, there is an equal and opposite reaction. Friction is a force that opposes sliding motion between two surfaces in contact. Mass, Weight, Density Mass is a measure of the amount of matter or substance in an object. Density is the mass per unit volume of a substance. Weight is the gravitational force acting on a mass. Gravitational field is a region in which a mass experiences a force due to gravitational attraction. Gravitational field strength is defined as the gravitational force acting per unit mass on an object. {eg. g =10N/kg}

Topics Definition Inertia of an object refers to the reluctance of the object to change its state of rest or motion due to its mass. Turning effect of Force Moment of a force is the product of force and the perpendicular distance from the pivot to the line of action of the force. Principle of moments states that when a body is in equilibrium, the sum of clockwise moments about a pivot is equal to the sum of anticlockwise moments about the same pivot. The centre of gravity of an object is defined as the point through which its whole weight appears to act. Stability refers to the ability of an object to return to its original position after it is slightly displaced. Energy, Work and Power Energy is the capacity to do work. Principle of conservation of energy states that energy can neither be created nor destroyed. It can be converted from one form to another or transferred from one body to another. Total energy in an isolated system remains constant. Work done by a constant force on an object is given by the product of the force and the distance moved by the object in the direction of the force. One Joule is the amount of work done by a force of 1 N which moves an object through a distance of 1 m in the direction of the force. Gravitational potential energy is the energy which a body possesses because of its position relative to the ground. Kinetic energy is the energy a body possessed due to its motion. Power is the rate of work done or rate of energy converted. Efficiency is the ratio of useful energy (or power) output over the total energy (or power) input and is usually expressed as a percentage. One watt is defined as the rate of work done or energy conversion of one joule per second. Renewable Energy is defined as energy from sources that can be replenished naturally. Pressure Pressure is defined as force per unit area. Atmospheric pressure is the weight of a layer of air that acts on the Earth per unit area. Temperature When two bodies are in thermal contact and there is no net flow of heat between them, they are said to be in thermal equilibrium. Temperature is a measure of the degree of hotness or coldness of a body. Heat refers to the amount of thermal energy that is being transferred from a hotter to a colder region.

Topics Definition Thermometric property is a measurable physical property that varies continuously and linearly with temperature. Ice point is the temperature of pure melting ice at one atmospheric pressure and is assigned a value of 00C. Steam point is the temperature of steam from water boiling at one atmospheric pressure assigned a value of 1000C. Kinetic Model of Matter Tiny particles in continuous motion is known as the kinetic model of matter. Brownian motion is the random motion of particles suspended in a fluid. Heat Transfer Heat refers to the amount of thermal energy that is transferred from a hotter to a colder region. Conduction is the process of thermal energy being transferred through a medium from one particle to another without any flow of the medium. Convection is the transfer of thermal energy by means of convection currents in a fluid (liquid or gas), due to a difference in density. Radiation is the transfer of thermal energy in the form of electromagnetic waves such as infrared radiation without the aid of a medium. Thermal Properties of Matter Internal Energy consists of kinetic energy (due to the motion of particles) and potential energy (due to the intermolecular forces) present in the molecules of a substance. Heat capacity C, is the amount of thermal energy required to raise the temperature of a body by 1 K or 1°C. (unit : J/K) Specific heat capacity, c, is the amount of thermal energy required to raise the temperature of unit mass of a material by 1 K or 1°C (J/kg ° C) Latent heat is the energy released or absorbed during a change of state, without a change in temperature. (unit : J) Latent heat of fusion, Lf of a solid is the amount of thermal energy required to change it from solid to liquid state, or vice versa, without any change in temperature. (unit : J) Specific latent heat of fusion lf of a solid is the amount of thermal energy required to change a unit mass of the solid to liquid, or vice versa, without a change in temperature. (unit : J/kg) Latent heat of vaporization, Lv, of a substance is the thermal energy required to change it from liquid to vapour state, or vice versa, without any change in temperature. (unit : J) Specific latent heat of vaporization, lv of a substance is the thermal energy required to change unit mass of a substance from liquid to vapour state, or vice versa, without any change in temperature (unit : J/kg)

Topics Definition Condensation is a change of state of a substance from gas to liquid and energy is released. Boiling is a process whereby a liquid changes to gas at constant temperature (its boiling point) Evaporation is a change of state of a substance from liquid to gas below boiling point. Freezing is a change of state when a substance changes from liquid to soild without any change in temperature. Melting is a change of state when a solid changes to a liquid upon heating at a constant temperature. Light First law of reflection states that the incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane. Second law of reflection states that the angle of incidence is equal to the angle of reflection. Angle of incidence is the angle between