IB Physics SL Definitions

Newton's First Law of Motion

an object at rest or in motion will stay at rest or in motion unless acted upon by an external unbalanced net force

Transitional Equilibrium

When the net force on an object is zero in all directions (i.e no linear acceleration)

Newton's Second Law of Motion

The net (or resultant) force acting on a body is equal to the product of its mass and its acceleration.

F=ma

Linear Momentum

The product of mass and velocity. A vector

units: kgms⁻¹

Impulse (2)

The change in momentum. A vector

unit: kgms⁻²

also product of Force and time

unit: Ns

Law of Conservation of Linear Momentum

The momentum of an isolated system remains constant. (i.e no external force acting)

Newton's Third Law of Motion

For every action on one object there is an equal but opposite reaction

Work

when a force moves an object in the direction of the force

unit: Joules (J)

Power

The rate of doing work (rate at which work is being performed

unit: Watt or Joule/second (W or Js⁻¹)

Kinetic Energy

energy an object has as a result of its motion

unit: Joules (J)

Gravitational Potential Energy

energy that is stored in an object by its height

unit: Joules (J)

Principle of Conservation of Energy

Energy is never created nor destroyed. It changes from one form to another.

Elastic Collision

KE and momentum conserved - no mechanical energy lost

ex: pool balls, ideal gas particles

Inelastic Collision

KE is not conserved, but momentum is.

Concept of Efficiency

the ratio of the useful energy to the total energy transferred

unit: none (%)

Centripetal motion (concepts)

direction is always changing therefore, so is acceleration and velocity

Centripetal Acceleration

The acceleration, directed toward the centre of a circle, which causes uniform circular motion

Centripetal Force

The force, directed toward the centre of a circle, which causes uniform circular acceleration.

Temperature

the average KE of the particle of a substance, which determines the direction of thermal energy transfer

unit: Kelvin (K)

Absolute Zero

The lowest temperature possible. -273˚C or 0K

Thermal Energy (+equations)

The non-mechanical transfer of energy between a system and its surroundings (naturally flows from hot to cold)

equations:

Q = mL

Q = mc(Tf-Ti)

unit: Joules (J)

Internal Energy

The energy contained in an object due to the random KE and PE of the molecules

unit: Joules (J)

Thermal Equilibrium

the state in which all parts of a system have reached the same temperature

Mole

The amount of a substance that contains the same number of particles as there are atoms in 12g of Carbon-12

units: mol

Avogadro constant

The number of particles in a mole. A=6.02x10^23

Molar Mass

The mass of 1mole of a substance

units: g/mol

Thermal Capacity

The amount of thermal energy (heat) required to raise the temperature of an object by 1K

equation: C= Q / (Tf - Ti)

unit: JK⁻¹

Specific Heat Capacity

The amount of thermal energy required to raise the temperature of 1Kg or a substance by 1K

equation: c = Q / m(Tf-Ti)

unit: Jkg⁻¹K⁻¹

Difference between Thermal and Specific Heat Capacity

specific heat is per unit mass, so thermal is the same as specific heat, multiplied by mass

Melting

Solid-liquid

Fusion

Liquid-solid

Vaporization

Liquid-gas

Difference between boiling and evaporating

boiling takes place throughout the liquid and always at the same temperature, evaporation takes place only at the surface of the liquid and can happen at all temperatures

Condensation

Gas-liquid

Sublimation

Solid-gas

Why does temp. not change during phase change?

Because the energy is being used to break or make bonds and so the energy is not turned into kinetic energy.

Specific Latent Heat (+formula)

the amount of energy required to change the state of 1kg of a substance

formula:

Q = mLf

Q = mLv

unit: Jkg⁻¹

Pressure

The force exerted per unit area

unit: Pascals (Pa)

Pressure and Temperature relationship

as Temperature increases, Pressure increases

directly proportional so P/T = constant

Pressure and Volume relationship

as Volume decreases, Pressure increase (as particles hit the container wall more frequently)

inversely proportional so P x V = constant

Volume and Temperature Relationship

as Volume increases, Temperature increases

directly proportional so V/T = constant

Combined Gas Laws (not Molecular)

P1V1T2 = P2V2T1 (# of molecules kept constant)

or (P1V1)/T1 = (P2V2)/T2

Molecular Gas Law

PV = kNT (N = number of molecules, T temp in K)

Ideal Gas

a gas that obeys all gas laws at any pressure, volume or temperature

formula: PV = nRT (n=number of moles)

Ideal Gas Law

PV = nRT (n = number of moles, T in K)

Kinetic Molecular Theory (FPICS)

F) no Forces act between the particles (stay in continous random motion) - Internal Energy = KE (no PE)

P) there is not loss in KE between particles and the container so all collisions are Perfectly elastic

I) all particles are Identical

C) all particles remain in Continuous random motion

S) there are many particles and they are extremely Small compared to the distance between each other

Simple harmonic motion (SHM) factors and equation

1) force or acceleration is always directed towards the centre

2) the force or acceleration is proportional to the distance from the centre

defining equation: a = -w²x

Displacement (Topic 4)

Distance from the equillibrium

unit: m

Amplitude

The maximum value for displacement from the mid point.

unit: m

Wavelength

the length of a full wave (the distance between two consecutive crests or any two consecutive points that are in phase); the distance traveled in one period

unit: m

Frequency

The number of oscillations per second

unit: hertz (Hz)

formula: 1 Hz = 1 oscillation per second.

Wave speed

the speed at which energy is transferred by the wave

unit: meters / second

Wave Intensity

the rate of energy transfer per unit area (for a wave, intensity is proportional to the square of the amplitude)

unit: Wm⁻²

Period (+formula)

The time taken for one oscillation

unit: seconds.

equation: T=1/frequency

Phase Difference

A way of comparing two oscillations by finding the difference between their phases.

Damping (Light & Critical)

Damping is a force that is always in the opposite direction to the direction of motion of the oscillating particle, the force is a dissipate force (it will eventually stop).

Light: gradual loss of total energy (ex: air resistance, water)

Critical: resistive forces so big that system returns to equilibrium without passing it (ex: in honey)

Natural Frequency of Vibration

The frequency that an object will oscillate at if it is moved from its equilibrium point and released.

Forced Oscillation

when an object is made to oscillate at another frequency than the natural frequency, by an external force

Resonance

when an oscillating system vibrates at the natural frequency (resonant frequency) of another system, causing it to vibrate and be amplified

Superposition

When two waves pass the same point at the same time, their displacements are added together to calculate the resultant displacement.

Transverse vs. Longitudinal Waves (Motion of Particles)

Transverse - particles of wave travel perpendicular to the direction of energy, Longitudinal - travel in parallel direction

Crest & Trough

Highest and lowest points of a transverse wave

Mechanical vs. Electromagnetic Waves (Medium required to travel?)

Mechanical waves need a medium to travel as they cannot travel through a vacuum and Electromagnetic waves can

Traveling vs. Standing Waves

Traveling waves carry energy as they move and have a constant amplitude, Standing waves neither move nor carry energy and have changing amplitudes

How are standing waves produced?

produced whenever two waves of identical frequency interfere with one another while traveling in opposite directions along the same medium.

Compression & Rarefaction

Highest and lowest pressure points (points bunched up vs. spread apart)

Anti-nodes

points at which crest meets crest (trough & trough)

Nodes

points at which there is no displacement (crest & trough)

Reflection (+formula)

when a wave hits a barrier and bounces off

formula: angle of incidence = angle of reflection

Refraction (+formula)

the bending of waves due to changing velocity, as a wave is travelling through different mediums

formula: index of refraction = c/v (velocity of light in a vacuum / velocity of light in that medium)

Angle of deviation

the difference between the angle of refraction and angle of incidence

Diffraction

takes place when a wave moves through a smaller opening (causes diffraction)

Constructive interference

in phase

Destructive interference

out of phase

Electric Potential Difference (+ formula)

The work done per unit charge moving a positive charge between two points in a circuit.

formula e.p.d = Work Done / Electric Charge

unit: Volts

Electron-Volt

The energy an electron gains by passing through a potential difference of 1 Volt, 1 eV = 1.6 x 10^-19 J

unit: Joules (J)

Electric Current

a flow of charge within a conductor

unit: Amperes

Ammeter (3)

the device that measures current

1) placed in series

2) very low resistance

3) in Amperes

Ampere (defined in terms of)

the force between two long current carrying wires

Resistance (+ relative to wire thickness & length)

the the ratio between the p.d. across the material to the current that flows through it

unit: Ohms

decreases when wire thicker

increases when wire longer

Voltmeter

the device that measures voltage

1) placed in parallel

2) very high resistance

3) in Volts

Work (Topic 5)

the amount of power supplied in a given time

units: kWh⁻¹

Ohm's Law

The potential difference is directly proportional to the current (provided that resistance stays constant)

Ohmic vs. non-ohmic behaviour

Non-ohmic does not behave Ohm's law as temperature increases, thus there is a loss in heat and resistance is not constant (ex: filament lamp)

Electromotive Force (EMF)

the work available (from an electrical source) per unit of charge

unit: Volts (V)

Difference between emf and (terminal) potential difference

emf is the energy available per unit charge, p.d. is the difference in energy dissipate per unit of charge

Internal Resistance

The resistance of the battery

Electrical Powers (3)

1) total power supplied by the cell : EI

2) the power dissipated in the cell : EI - VI = I^2 r

3) the power dissipate in the external circuit: VI

The 3 types of Sensors

1) LDR (Light Dependent Resistor)

Light increases, Current increases, Resistance decreases

2) Thermistors (NTC - Negative Temperature Coefficient)

Temperature increases, Current increases, Resistance decreases

3) Strain Gauge (length increases when under strain)

Length increases, cross-sectional Area decreases, Resistance increases

Potential Divider - 3 part definition

1) divides potential difference

2) acts like multiple resistors in series

3) to control voltages

Newton's Universal Law of Gravitation

The force of gravity between two objects is directly proportional to the product of the two masses and inversely proportional to the square of the distance between them and acts along a line joining their centers. (Note: The objects are point masses. If they are not point masses but are very far apart, that is, the distance between them is very much greater than their radii, they can be treated like point masses)

(F=G m₁m₂/r²)

Gravitational Field Strength

Gravitational force per unit mass on a point mass (g=F(g)/m)

Gravitational Potential Energy

The work done in moving a mass from infinity to a point in space (Note: The work done is path independent).

Weightlessness in free-fall

A sensation of weightlessness because a person is falling freely toward the Earth, hence there is no normal force (reaction force) acting on the person due to gravity.

Weightlessness in orbital motion

A sensation of weightlessness due to the spacecraft and all objects in it being in constant free-fall together as they circle Earth.

Law of Conservation of Change

The total electric charge of an isolated system remains constant.

Conductor

Material through which electric charge flows freely.

Insulator

Material through which electric charge does not flow freely.

Coulomb's Law

The electric force between two point charges is directly proportional to the product of the two charges and inversely proportional to square of the distance between them, and directed along the line joining the two charges (F = kq₁q₂ / r²).

Electric Field Strength (E)

Electric force per unit charge experienced by a small positive test charge

(E=F/q)