# SPM Physics Terms and Definition

July 18, 2017 | Author: yihtang | Category: Waves, Radioactive Decay, Atomic Nucleus, Nuclear Physics, Atoms

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Chapter 1: Introduction to Physics Physical quantities

QUANTITIES that are measurable

Base quantities

PHYSICAL QUANTITIES that cannot be defined in terms of other physical quantities but has its own definition

Derived quantities

PHYSICAL QUANTITIES that are derived from base quantities by multiplication or division or both

Scientific notation/ standard form

POWERS of the base number 10 to show a very large or small number

Prefixes

GROUP OF LETTERS placed at the beginning of a word to modify its meaning, which act as multipliers

Scalar quantity

QUANTITY which has only magnitude or size (time, temperature, mass, volume, distance, density, power)

Vector quantity

QUANTITY which has both magnitude or size and direction (force, velocity, displacement, acceleration, momentum)

Error

DIFFERENCE between actual value of a quantity and the value obtained in measurement

Systematic errors

CUMULATIVE ERRORS that can be corrected, if the errors are known. (zero error, incorrect calibration of measuring instrument)

Random errors

ERRORS that arise from unknown and unpredictable variations in condition, and will produce a different error every time. Random errors are caused by factors that are beyond the control of observers. (human limitations, lack of sensitivity, natural errors, wrong technique)

Zero error

ERROR that arises when the measuring instrument does not start from exactly zero

Parallax error

ERROR in reading an instrument because the observer’s eyes and the pointer are not in a line perpendicular to the plane of scale

Measurement

PROCESS of determining value of a quantity using a scientific instrument with a standard scale

Consistency

ABILITY to register the same reading when a measurement is repeated (improve – eliminates parallax error, greater care, not detective instrument)

Accuracy

DEGREE to which a measurement represents the actual value (improve – repeat readings, avoid parallax/zero error, high accuracy instrument)

Sensitivity

ABILITY to detect quickly a small change in the value of a measurement (thermometer – thin wall bulb, narrow capillary)

Inferences

EARLY CONCLUSION that you draw from an observation or event using information that you already have on it

Hypothesis

GENERAL STATEMENT that is assumed to be true regarding the relationship between the manipulated variable and responding variable

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Chapter 2: Forces and Motion Distance

how far a body travels during motion

Displacement

CHANGE IN POSITION of an object from its initial position in a specified direction

Speed

RATE OF CHANGE of distance

Velocity

RATE OF CHANGE of displacement

Mass

MEASURE of an object’s inertia AMOUNT of matter in the object

Acceleration

RATE OF CHANGE of velocity

Inertia

PROPERTY of matter that causes it to resist any change in its motion or state of rest

Momentum

PRODUCT of mass and velocity

Force

pulling or a pushing ACTION on an object

Impulsive force

LARGE FORCE which acts over a very short time interval RATE OF CHANGE in momentum

Gravity

FORCE originated from centre of the Earth that pulls all objects towards the ground

Free fall

FALLING of an object without encountering any resistance from a height towards the earth with an acceleration due to gravity

Forces in equilibrium

An object is said to be in a state of equilibrium when forces act upon an object and it remains stationary or moves at a constant velocity

Resultant force

SINGLE FORCE which combines two or more forces which act on an object

Work

Work is done when a force causes an object to move in the direction of the force.

Energy

CAPACITY of a system to do work

Gravitational PE ENERGY STORED in the object because of its height above the earth surface Elastic PE

ENERGY STORED in the object as a result of stretching or compressing it

Kinetic energy

ENERGY possessed by a moving object

Power

RATE at which work is done or energy is changed and transferred

Efficiency

ABILITY of an electrical appliance to transform energy from one form to another without producing useless energy or wastage

Elasticity

PROPERTY of an object that enables it to return to its original shape and dimensions after an applied force is removed

Spring constant

FORCE needed to extend a spring per unit length

Elastic limit

MAXIMUM STRETCHING FORCE which can be applied to an elastic material before it ceases to be elastic

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PRINCIPLE Hooke’s Law

Hooke’s law states that the force, F applied to a spring is directly proportional to the spring’s extension or compression, x, provided the elastic limit is not exceeded.

Principle of conservation of energy

Principle of conservation of energy states that total energy in an isolated system is neither increased nor decreased by any transformation. Energy cannot be created nor destroyed, but it can be transformed from one kind to another, and the total amount stays the same.

Principle of conservation of momentum

The principle of conservation of momentum states that, in any collision or interaction between two or more objects in an isolated system, the total momentum of the system will remain constant; that is, the total initial momentum will equal the total final momentum.

Newton’s first law of motion

Newton’s first law of motion states that a body will either remain at rest or continue with constant velocity unless it is acted on by an external unbalanced force.

Newton’s second law of motion

Newton’s second law of motion states that the acceleration a body experiences is directly proportional to the net force acting on it, and inversely proportional to its mass. F =ma

Newton’s third law of motion

Newton’s third law of motion states that to every action there is an equal but opposite reaction.

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Chapter 3: Forces and Pressure Pressure

FORCE acting normally on a unit surface area

Gas pressure

FORCE per unit area exerted by the gas particles as they collide with the walls of their container (due to the rate of change of momentum)

Buoyant force

NET FORCE acting upwards due to the difference between the forces acting on the upper surface and the lower surface

PRINCIPLE Law of Flotation

Law of floatation states that the weight of an object floating on the surface of a liquid is equal to the weight of water displaced by the object. (weight of object = weight of water displaced)

Pascal’s Principle

Pascal’s principle states that a pressure applied to a confined fluid is transmitted uniformly in all directions throughout the fluid.

Archimedes’ principle

Archimedes’ principle states that the buoyant force on a body immersed in a fluid is equal to the weight of the fluid displaced by that object (buoyant force = weight of water displaced)

Bernoulli’s principle

Bernoulli’s principle states that the pressure of a moving fluid decreases as the speed of the fluid increases, and the converse is also true.

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Chapter 4: Heat Temperature

DEGREE of hotness of an object

Thermometric property

PHYSICAL PROPERTY of a substance which is sensitive to and varies linearly with the temperature change

Thermal equilibrium

A STATE when heat transfer between the two objects are equal and the net rate of heat transfer between the two objects are zero

Heat capacity

HEAT ENERGY required to raise its temperature by 1°C or 1 K

Specific heat capacity

HEAT ENERGY required to produce 1°C or 1 K rise in temperature in a mass of 1 kg.

Latent heat

HEAT ABSORBED OR RELEASED when a substance changes its state without a change in temperature is called the latent heat of the substance

Specific latent heat of fusion

HEAT ENERGY required to change 1 kg of a substance from solid state to liquid state, without a change in temperature

Specific latent heat of vapourisation

HEAT ENERGY required to change 1 kg of a substance from liquid state to gaseous state, without a change in temperature

PRINCIPLE Boyle’s Law

Boyle’s Law states that the pressure of a fixed mass of gas is inversely proportional to its volume provided the temperature of the gas is kept constant (PV = k)

Pressure Law

The pressure law states that the pressure of a fixed mass of gas is directly proportional to its absolute temperature (in Kelvin), provided the volume of the gas is kept constant (P/T = k)

Charles’ Law

Charles’ law states that the volume of a fixed mass of gas is directly proportional to its absolute temperature (in Kelvin), provided the pressure of the gas is kept constant (V/T = k)

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Chapter 5: Light Refraction

PHENOMENON where the direction of light is changed when it crosses the boundary between two materials of different optical densities as a result of a change in the velocity of light.

Apparent depth, d

DISTANCE of the image from the surface of water (or the boundary between the two mediums involved)

Real depth, D

DISTANCE of the object from the surface of the water (or the boundary between the two mediums involved)

Total internal reflection

TOTAL REFLECTION of a beam of light at the boundary of two mediums, when the angle of incidence in the optically denser medium exceeds a specific critical angle

Critical angle

GREATEST ANGLE OF INCIDENCE in the optically denser medium for which the angle of refraction, r = 90°

Power of lens

MEASURE OF ITS ABILITY to converge or diverge an incident beam of light

PRINCIPLE Laws of Reflection

- the angle of incidence, i, is equal to the angle of reflection, r (i = r) - the incident ray, normal and reflected ray will all lie in the same plane

Law of Refraction

- The incident ray and the refracted ray are on the opposite sides of the normal at the point of incidence, all three lie in the same plane - Obey snell’s law

Snell’s Law

The value of sin i is a constant. sin r

IMAGE CHARACTERISTICS Virtual an image which cannot be projected (focused) onto a screen Real an image which can be projected (focused) onto a screen Laterally inverted an image which left and right are interchanged Upright an image which in vertical position Diminished image formed is smaller than the object Magnified image formed is larger than the object

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Chapter 1 – Waves Waves

A TYPE OF DISTURBANCE produced by an oscillating or vibrating motion in which a point or body moves back and forth along a line about a fixed central point produces waves.

Wavefront

LINE OR PLANE on which the vibrations of every points are in phase and are at the same distance from the source of the wave. In phase = same direction, same displacemen

Transverse Wave

WAVE in which the vibration of particles in the medium is perpendicular to the direction of propagation of the wave (water waves, light waves, electromagnetic waves)

Longitudinal Wave

WAVE in which the vibration of particles in the medium is parallel to the direction of propagation of the wave (sound waves, ultrasound)

Amplitude

MAXIMUM DISPLACEMENT form its equilibrium position MEASURE of height of the wave crest or depth of the wave trough.

Period

TIME TAKEN to complete an oscillation, from one extreme point to the other and back to the same position.

Frequency

NUMBER OF COMPLETE OSCILLATIONS made by a vibrating system in one second

Wavelength, λ

DISTANCE between successive points of the same phase in a wave

Damping

DECREASE in the amplitude of an oscillating system is called damping. (Internal damping: extension and compression of molecules External damping: frictional force/ air resistance) a↓;f=

Resonance

Resonance occurs when a system is made to oscillate at a frequency equivalent to its natural frequency by an external force. The resonating system oscillates at its maximum amplitude.

Natural frequency

FUNDAMENTAL FREQUENCY of which an object vibrates. It is the frequency of a system which oscillates freely without external force

Reflection of wave

Reflection of wave occurs when a wave strike an obstacle direction ≠ ; f = ; a = ; λ =

Refraction of wave

Refraction of wave occurs when a wave travel from one medium to another f = ; v ≠ ; λ ≠ ; direction ≠

Diffraction of waves

PHENOMENON in which waves spread out as they passed through an aperture or round a small circle f = ; λ = ; speed = ; v ≠ ; direction ≠

Interference of waves

SUPERPOSITION of two waves originating from two coherent sources coherent = same frequency, amplitude and in phase

Constructive interference

Constructive interference occurs when the both crests or both troughs of both waves coincide to produce a wave with crests and troughs of maximum amplitude

Destructive interference

Destructive interference occurs when the crest of one wave coincides with the trough of the other wave, thus cancelling each other with the result that the resultant amplitude is zero.

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Antinode

POINT where constructive interference occurs.

Node

POINT where destructive interference occurs.

Electromagnetic waves

PROPAGATING WAVES in space with electric and magnetic components. These components oscillate at right angles to each other and to the direction of propagation of wave.

Monochromatic light

LIGHT with only one wavelength and colour

PRINCIPLE Principle of superposition

Principle of superposition states that at any instant, the wave displacement of the combined motion of any number of interacting waves at a point is the sum of the displacements of all the components waves at that point.

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Chapter 2 – Electricity Charge, Q

WORK DONE to move a unit of voltage in a circuit

Current, I

RATE of flow of charge

Potential difference, V

WORK DONE in moving one coulomb of charge from one point to another in an electric field

Electric field

A FIELD in which electric charge experiences an electric force A FIELD in which electric force acts in a particle with electric charge

Circuit

CLOSED LOOP through which charge can continuously flow

Resistance, R

RATIO of the potential difference across the conductor to the current flowing through it MEASURE of the ability of the conductor to resist the flow of an electric current through it

Superconductor CONDUCTOR in which its resistance will suddenly become zero when it is cooled below a certain temperature called the critical temperature

Electromotive force (e.m.f.)

TOTAL ENERGY supplied by a cell to move a unit of electrical charge from one terminal to the other through the cell and the external circuit

Power rating

RATE at which it consumes electrical energy.

PRINCIPLE Ohm’s Law

Ohm’s law states that the electric current, I flowing through a conductor is directly proportional to the potential difference across the ends of conductor, if temperature and other physical conditions remain constant. That is, ܸ ‫ܫ ן‬

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Chapter 3 – Electromagnetism Electromagnet

DEVICE in which magnetism is produced by an electric current TEMPORARY MAGNET which acts as a magnet when the current is switched on and ceases to be a magnet when the current is switched off

Magnetic field

REGION in which a magnetic material experiences a force as the result of a magnet or a current-carrying conductor

MAGNETIC FIELD with the field lines pointing towards or away from the centre of a circle.

Electromagnetic induction

PRODUCTION of an electric current by a changing magnetic field (conductor cuts across a magnetic flux –OR– a change of magnetic flux linkage with a coil)

Root mean square current/ voltage

VALUE of a steady current/ voltage, which would produce the same heating effect in a given resistor.

Transformer

EQUIPMENT to raise or lower the potential difference of an alternating current supply

The magnitude of the induced electromotive force (e.m.f.) is directly proportional to the rate of change of magnetic flux linkage with the solenoid or the rate at which a conductor cuts through the magnetic flux.

Lenz’s Law

Lenz’s law states that an induced electric current always flows in such a direction so as to oppose the change (or motion) producing it.

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Chapter 4 – Electronics Thermoionic emission

EMISSION of electrons from hot metal surface

Work function

MINIMUM ENERGY required to eject electrons from surface

Cathode ray

fast moving ELECTRONS travel in a straight line in vacuum

Cathode ray oscilloscope

measuring and testing INSTRUMENT used in study of electricity and electronics

MATERIAL which allows current to flow thorugh them Conductor Semiconductor MATERIAL whose resistance is between good conductor and insulator MATERIAL which does not conduct electric current Insulator

Junction voltage

POTENTIAL DIFFERENCE acting from n-type to p-type material of a diode across the depletion layer

Rectification

CONVERSION of a.c. to d.c. by diode

Smoothing

PROCESS where output is smoothed by connecting a capacitor across load that acts as a reservoir and maintains potential difference across load

Logic gates

ELECTRONIC SWITCHES with one or more inputs and one output.

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An atom consists of a nucleus which is made up of protons and neutrons, with electrons orbiting the nucleus.

Nuclide

TYPE of nucleus with particular proton number and nucleon number

Proton number

NUMBER of protons in the nucleus of an atom

Nucleon number

NUMBER of protons and neutrons in an atom

Isotopes

ATOMS of an element which have the same proton number but different nucleon number (similar chemical properties but differs in physical properties)

SPONTANEOUS DISINTEGRATION of unstable nucleus into a more stable nucleus with the emission of energetic particles or protons

PROCESS where an unstable nucleus becomes a more stable nucleus by emitting radiations

ISOTOPE that has unstable nucleus that tends to undergo radioactive decay

Half life

TIME TAKEN for the activity of atoms to fall to half its original value TIME TAKEN for half the atoms in a given sample to decay

Nuclear fission

PROCESS involving the splitting of a heavy nucleus into two nuclei of roughly equal mass and shooting out several neutrons at the same time.

Nuclear fusion

PROCESS involving the fusion of two or more small and light nuclei come together to form a heavier nucleus.

PRINCIPLE Einstein’s Principle of Mass-Energy Conservation

The change of energy is linked to the change of mass by the equation ‫ ܧ‬ൌ ݉ܿ ଶ

(C) Yeo Yih Tang 2009. Mail: [email protected]