List of definitions

Prepared by: Lim Kang Hui ‘O’ Level Physics List of Definitions Term Definition 1 Measurement 1.1 Scalar A scalar quantity has a magnitude but no direction. 1.2 Vector A vector quantity has a magnitude and direction. 1.3 Precision Measure of how close a set of readings of the same physical quantity with each other 1.4 Accuracy Measure of how close a set of readings are to the true value. 2 Kinematics 2.1 Distance Length of path taken. 2.2 Displacement Net change in position of an object. 2.3 Freefall An object is in freefall when the only force acting on it is due to gravity. 2.4 Terminal Velocity A constant speed (with zero acceleration) at when the drag force of an object due to air resistance equals to the weight of the object such that it experiences zero net force. 3 Dynamics 3.1 Force A push or a pull on a body. 3.2 Newton’s first law of motion Every object will continue in its state of rest or uniform motion in a straight line unless a resultant force act on it. 3.3 Newton’s second law of motion When a resultant force acts on an object of a constant mass, the object will accelerate in the direction of the resultant force. The product of the mass m and acceleration anet of the object gives the resultant force. 3.4 Newton’s third law of motion If Body A exerts a force onto Body B, Body B will exert and equal and opposite force onto Body A. 3.5 Equilibrium Body is in equilibrium if the net force on the body is zero. (i.e., static system where no net acceleration takes place). 3.6 Normal force A component of the contact force that is perpendicular to the surface the object is in contact with. 3.7 Friction force A contact force that opposes or tends to oppose motion between surfaces in contact. 4 Mass, Weight, and Density 4.1 Mass Amount of matter in a body. 4.2 Inertia Reluctance of the object to change its state of rest or motion, due to its mass. 4.3 Weight Amount of force of gravity acting on an object. 4.4 Density Mass per unit volume 5 Turning Effect of Forces 5.1 Moment Product of a force F and the perpendicular distance from the pivot to the line of action of the force F. 5.2 Principle of moments When a body is in equilibrium, the sum of clockwise moments about a pivot is equal to the sum of anti-clockwise moments about the same pivot. 5.3 Centre of gravity Is a point where the weight of an object seems to be acting on, the centre of gravity can lie outside of an object. 5.4 Stability Measure of its ability to return to its original position after it is slightly displaced.

Prepared by: Lim Kang Hui 6 Pressure 6.1 Pressure Amount of force acting per unit area. 6.2 Atmospheric pressure Pressure at sea level (i.e., 1 atm = 101325 Pa = 760 mmHg = 76 cmHg) 7 Energy, Work, and Power 7.1 Energy Capacity to do work. 7.2 Principle of conservation of energy Energy cannot be created nor destroyed, but can be converted from one form to another. Total energy in an isolated system is a constant. 7.3 Kinetic energy Energy an object possesses when it is moving. Given as !"𝑚𝑣". 7.4 Gravitational potential energy Amount of work can be done by gravitational force from height h away. Given as 𝑚𝑔ℎ. 7.5 Mechanical energy Mechanical energy of an object is the sum of its kinetic energy and its gravitational potential energy. 7.6 Work done Work done by a constant force on an object is the product of force F and the distance (displacement) moved by the object in the direction of the force. 7.7 Power Rate of work done. 8 Kinetic Model of Matter 8.1 Brownian Motion Random movement of microscopic particles suspended in a fluid (gas or liquid) caused by collisions with molecules of the surrounding. 8.2 Charles Law Pressure of a gas is directly proportional to its temperature if the volume stays constant. 8.3 Boyle Law Pressure of a gas is inversely proportional to the volume of gas if the temperature stays constant. 8.4 Guy-Lussac Law Volume of a gas is directly proportional to its temperature if the pressure stays constant. 9 Transfer of Thermal Energy 9.1 Conduction Heat transfer in a medium without the movement of the medium itself. 9.2 Convection Heat transfer in a medium by the movement of particles in it. 9.3 Radiation Transfer of heat energy by infrared waves, one of the components of electromagnetic waves. 10 Temperature 10.1 Temperature Measure of degree of hotness or coldness of a body. 10.2 Thermometric property Object is said to have thermometric property if it experiences a measurable change in its physical property which varies continuously and linearly (i.e., monotonically) with the change in temperature. 11 Thermal Properties of Matter 11.1 Internal Energy Particles in matter possess internal energy which is made out of kinetic energy and potential energy of the particles. 11.2 Heat capacity Amount of heat required to raise the temperature of an object by 1 oC (or 1 K). 11.3 Specific heat capacity Amount of heat required to raise the temperature of an object of mass 1 kg by 1 oC (or 1 K). 11.4 Latent heat Total heat energy absorbed or released when a substance changes its physical state completely at a constant temperature.

Prepared by: Lim Kang Hui 12 General Wave Properties 12.1 Wave A wave is defined as a process of transferring energy from one location to another which is produced by an oscillating or vibrating motion. 12.2 Transverse wave A transverse wave is when the particles oscillate perpendicular to the direction of propagation. (e.g., water waves, electromagnetic wave). 12.3 Longitudinal wave A longitudinal wave is when the particles oscillate parallel to the direction of propagation. (e.g., sound wave). 12.4 Wavelength Distance between two adjacent points of the same phase on a wave. 12.5 Amplitude Maximum displacement of a particle from its equilibrium position in a wave. 12.6 Wavefront An imaginary line on a wave that joins all adjacent points (of the crest or trough) that are in phase. 12.7 Period Time taken for one complete wavelength. 12.8 Frequency Number of complete wavelengths produced in one second. 12.9 Compression A compression in a longitudinal wave is where there are more particles around that region than in equilibrium. 12.10 Rarefraction A rarefraction in a longitudinal wave is where there are less particles around the region than in equilibrium. 12.11 Angle of incidence Angle between the direction of propagation of incident wave and the normal. 12.12 Angle of reflection Angle between the direction of propagation of reflected wave and the normal. 13 Light 13.1 First law of reflection The incident ray, reflected ray, and the normal lie on the same plane. 13.2 Second law of reflection In reflection, the angle of incidence is equal to the angle of reflection. 13.3 Reflected image Formation of image in a plane mirror is due to the reflection of light. Characteristics of reflected image: 1) Virtual: An image that cannot be captured on a screen 2) Upright 3) Laterally inverted 4) Same size as the object 5) Same distance from the mirror 13.4 Refraction Bending of light as light passes from one optical medium to another, due to light changing speed. 13.4 First law of refraction The incident ray, refracted ray, and the normal lie on the same plane. 13.5 Second law of refraction For two given media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant (refractive index). i.e., 𝑛=)*+,)*+- 13.6 Refractive index Refractive index of a medium is the ratio of the speed of light in vacuum (or air) to the speed of light in the medium.

Prepared by: Lim Kang Hui 13.7 Critical angle Angle of incidence which gives rise to an angle of refraction of 90o. (Only takes place when light travels from a denser medium to a less dense medium) i.e., sin𝑐= !3 13.8 Total internal reflection Total reflection of light ray at the boundary of two media when the angle of incidence in the optically denser medium exceeds the critical angle. (Occurs when an incident ray is reflected back