Definitions, Laws and Equations for CSEC Physics

Principal Focus

It is the point where light rays parallel and close to the principal axis converge or appear to diverge.

Kinetic energy

Kinetic energy is a form of energy that an object or a particle has by reason of its motion.

Critical Angle

The minimum angle of incidence for which a light ray is totally reflected within a medium. It is the angle of incidence that produces an angle of refraction of 90 degrees.

Frequency

The time to produce a complete wave cycle is the period, T. Its unit is seconds, s.

Refractive Index

When light travels from one medium to another, it will bend at the boundary of the two media. The amount of bending depends on the refractive indexes of the two medium.

Alpha Particle

A cluster of 2 protons and 2 neutrons emitted from a nucleus in one type of radioactivity. It is also a helium nucleus emitted by some radioactive substances, originally regarded as a ray.

Beta particles

A negatively charged particle (an electron) emitted from the nucleus of an atom during radioactive decay.

Vector quantity

A vector quantity is a quantity characterized by both a magnitude and a direction. For example velocity, force, acceleration, and moment are all vector quantities. The magnitude (sometimes referred to as the norm) of a vector is a positive scalar.

Focal length of a lens

It is the distance from the center of the lens to the focal point measured along the optic axis. In simple terms it is a specific zoom position.

Lenz's Law

Lenz's Law can be used to predict the direction of the induces e.m.f. or current. For example, if a north pole of a magnet is pushed towards a coil, the induced current is in such a way that it produces a north on the side of the coil facing the magnet. This is to oppose the incoming magnet. Thus, the current will be in anti-clockwise direction. Similarly, if the north pole of a magnet is pulled away from a coil, the induced current is in such a way that it produces a south on the side of the coil facing the magnet. This is to oppose the change and to attract the magnet back. Thus, the current will be a clockwise direction.

Wave speed

Let's assume that the wavelength of a transverse wave in a slinky spring is 0.4 m and it takes 1 second for a particular crest to travel 0.8 m (equivalent to two wavelengths 2λ)

Law of Electrostatics

Like charges repel each other; unlike charges attract. Thus, two negative charges repel one another, while a positive charge attracts a negative charge

Momentum

Momentum is the product of the mass of a particle and its velocity.

Newton's First law

Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.

Ohm's Law

Ohm's Law states that the current flowing through a conductor is directly proportional to the the potential difference across its ends provided all other physical conditions (e.g. temperature) remain constant.

Law of Magnetism

Opposite magnetic poles attract and like magnetic poles repel.

Power

Power in mechanical systems is the combination of forces and movement. In particular, power is the product of a force on an object and the object's velocity, or the product of a torque on a shaft and the shaft's angular velocity.

Watt

Power in mechanical systems is the combination of forces and movement. In particular, power is the product of a force on an object and the object's velocity, or the product of a torque on a shaft and the shaft's angular velocity.

Pressure

Pressure is a measure of the average force per unit area acting on the wall as a result of the molecules' change in momentum during collisions with the wall.

Principle of Conservation of Momentum

Principles of conservation of momentum states that two or more bodies in an isolated system acting upon each other, their total momentum remains constant unless an external force is applied.

Relative Density

Relative density or density index is the ratio of the difference between the void ratios of a cohesion less soil in its loosest state and existing natural state to the difference between its void ratio in the loosest and densest states.

Scalar quantity

Scalar, a physical quantity that is completely described by its magnitude. Examples of scalars are volume, density, speed, energy, mass, and time. Other quantities, such as force and velocity, have both magnitude and direction and are called vectors.

Pitch

Sounds are higher or lower in pitch according to the frequency of vibration of the sound waves producing them. A high frequency (e.g., 900 hertz [Hz; cycles per second]) is perceived as a high pitch and a low frequency (e.g., 48 Hz) as a low pitch.

Law of Moments

The Law of Moments states that when a body is balanced, the total clockwise moment about a point equals the total anticlockwise moment about the same point. Moment =force F x perpendicular distance from the pivot d.

GAS LAWS

The behaviour of a fixed gas can be described by three laws, namely Boyle's Law, Charles' Law and the Pressure Law.

Centre of gravity

The center of gravity is the point through which the force of gravity acts on an object or system. In most mechanics problems the gravitational field is assumed to be uniform. The center of gravity is then in exactly the same position as the center of mass.

Right Hand Grip Rule

The direction of the magnetic field in a long current-carrying wire can be determined by using the right-hand grip rule. The method is to grip the wire using the right hand with the thumb pointing in the direction of the current. The flexed fingers will point in the same direction as the field lines.

Amplitude

The distance moved by a particle from its equilibrium position is also called its displacement. The maximum displacement moved by a particle in a wave is called its amplitude, A. The unit for displacement and amplitude is metres, m.

Constant acceleration equations of motion(4 eqns)

The equations are as follows: v=u+at,s=(u+v2)t v2=u2+2as s=ut+12at2 s=vt−12at2.

Lens Formula

The formula for lens: 1/focal length = 1/object distance + 1/image distance

Heat Capacity

The heat capacity, C, of an object is defines as the amount of thermal energy required to increase the temperature of the object by one unit rise in temperature. The Sl unit for heat capacity is Joule per Kelvin, or J K^-1.

Loudness

The larger amplitude means a louder sound, and a smaller amplitude means a softer sound.

Hooke's Law

The law stating that the stress of a solid is directly proportional to the strain applied to it. Equation: F=-kx

Boyle's Law

The law that states that the pressure of a gas with fixed mass and fixed temperature is inversely proportional to its volume. In symbols, P ∝ 1/V or PV = k where P is the pressure V is the volume for a fixed mass of gas; and K is a constant

Pressure Law

The law that states that the pressure of a gas with fixed mass and fixed volume is directly proportional to its temperature. In symbols, P ∝ T or P/T = k where P is the pressure; T is the temperature in Kelvin scale for a fixed mass of gas; and k is a constant

Charles' Law

The law that states that the volume of a gas with fixed mass and fixed pressure is directly proportional to its temperature. In symbols, V ∝ T or V/T = k where V is the volume; T is the temperature in Kelvin scale for a fixed mass of gas; and k is a constant

Faraday's 2nd Law

The masses of different ions liberated at the electrodes, when the same amount of electricity is passed through different electrolytes are directly proportional to their chemical equivalents.

Quality

The more energy a wave has, the higher its amplitude. As amplitude increases, intensity also increases.

Efficiency

The percentage of the input work that is converted to output work. Efficiency, E = Output Value/Input Value x 100%

Principle of Conservation of Energy

The principle of energy conservation states that energy is neither created nor destroyed. It may transform from one type to another. Like the mass conservation principle, the validity of the conservation of energy relies on experimental observations; thus, it is an empirical law.

Snell's Law

The ratio of the sines of the angles of incidence and refraction of a wave are constant when it passes between two given media. In general, Snell's law can be expressed as n (subscript)1 sin 0 (subscript)1 = n (subscript)2 sin 0 (subscript)2

Resistors In Series

The reading for all ammeters are the same. This means that the current flowing through resistors in series is the same. l = l (subscript)1 = 1 (subscript)2 = l (subscript)3 The sum of the reading of voltmetres 1, 2 and 3 is equal to voltmetre 4. This means the total potential difference across all three resistors is the sum of potential difference across each resistor. V = V (subscript)1 = V (subscript)2 = V (subscript)3 Applying V = IR V = IR (subscript)1 + IR (subscript)2 + IR (subscript)3

Resistors In Parallel

The reading for all voltmetres are the same. This means that the potential differences across resistors in parallel are the same. V = V (subscript)1 = V (subscript)2 = V (subscript)3 The sum of the readings of ammetres 1, 2and 3 is equal to the readings of ammetres 4 and 5. This means that the sum of currents in the resistors in a parallel circuit is equal to the current entering or leaving the parallel junction. I = I (subscript)1 = I (subscript)2 = I (subscript)3 Applying I = V/R I = V/R (subscript)1 + V/R (subscript)2 + V/R (subscript)3 I/V = (1/R (subscript)1 + 1/R (subscript)2 + 1/R (subscript)3)

Specific Heat Capacity

The specific heat capacity of an object or substance is defined as the amount of thermal energy required to increase the temperature of one unit mass of the object by one unit. The Sl unit for specific heat capacity is Joule per kg per Kelvin, or J kg^-1 K^-1.

Specific Latent Heat of Fusion

The specific latent heat of fusion, l (subscript)f, for a substance is defined as the amount of thermal energy required to change one unit mass of the substance from solid to liquid without a change in temperature. The Sl unit for latent heat is Joule per kilogram, or J kg^-1

Specific Latent Heat Of Vaporisation/Evaporation

The specific latent heat of vaporisation, l (subscript)v, for a substance is defined as the amount of thermal energy required to change one unit mass of the substance from solid or liquid to gas without a change in temperature.

Fleming's Left hand rule

The thumb points to the direction the force acts on the wire. The index finger points to the direction of the magnetic field. The middle finger points to the direction of current flow. All three perpendicular to each other.

Moment

The turning effect of the force on the body on which it is acting is measured by the moment of a force. The moment of a force depends on the magnitude of the force and the distance from the axis of rotation.

Wave Length

The wavelength, λ, is the minimum distance between two points in a wave in which the wave repeats itself, Its unit is metres, m.

Work

Work is the energy transferred to or from an object via the application of force along a displacement. Equation: W = Fs W =work F =force s =Displacement

Fleming's right hand rule

Fleming's right-hand rule gives which direction the current flows. The right hand is held with the thumb, index finger and middle finger mutually perpendicular to each other (at right angles), as shown in the diagram. The thumb is pointed in the direction of the motion of the conductor relative to the magnetic field.

Gamma Rays

Gamma rays are electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei.

Half-Life

Half-life is the time taken for the number of atoms to decay (or the rate of disintegration) to halve its original starting value at any point in time.

Newton's Second law

His second law defines a force to be equal to change in momentum (mass times velocity) per change in time. Momentum is defined to be the mass m of an object times its velocity V.

Newton's Third law

His third law states that for every action (force) in nature there is an equal and opposite reaction. If object A exerts a force on object B, object B also exerts an equal and opposite force on object A.

Transverse Wave

If a slinky is stretched on the floor and fixed at one of its ends, it can effectively demonstrate a transverse wave. If the slinky is given a sideway flick at the loose end, a disturbance called a pulse can be seen travelling along the spring.

Longitudinal Wave

If one end of the slinky is flicked along the length of the slinky, another form of wave energy travelling through the slinky is observed. This is a longitudinal wave.

Gravitational Potential Energy

In classical mechanics, the gravitational potential at a location is equal to the work (energy transferred) per unit mass that would be needed to move an object to that location from a fixed reference location.

Acceleration

In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by the orientation of the net force acting on that object.

Isotope

Isotopes of the same element have the same number of protons in the nucleus but different number of neutrons.

Mass number

Atomic mass number or nucleon number, A, is the number of nucleons found in the nucleus. Nucleons refer to the protons and neutrons in the nucleus.

Atomic number

Atomic number or proton number, Z, is the number of protons found in the nucleus.

Average Speed

Average speed is a rate. In kinematics, a rate is always a quantity divided by the time taken to get that quantity (the elapsed time). Since average speed is the rate position changes, average speed = distance traveled/time taken.

Average velocity

Average velocity is a vector quantity. Average velocity is defined as the change in position or displacement (∆x) divided by the time intervals (∆t) in which the displacement occurs. The average velocity can be positive or negative depending upon the sign of the displacement.

Density

Density is the mass per unit volume of a substance or object, defined as ρ=m/V. The SI unit of density is kg/m3. kg/m 3 . Pressure is the force per unit perpendicular area over which the force is applied, p=F/A.