Super Important Core IB Physics Knowledge (Topics 1-8)

Work

The transfer of energy, measured in joules. W = ΔE

Power

The rate of the transfer of energy, measured in joules per second. P = ΔE/Δt

Unit definition of a Watt

1 W = 1 J/s (Joule per second)

Unit definition of a Volt

1 V = 1 J/C (Joule per Coulomb)

Formula for the weight of an object

W = mg (AKA Fg = mg, only works on Earth's surface)

Internal energy

Total random kinetic and potential energy of the particles in a substance

Specific heat capacity

Energy required to raise the temperature of 1 kg of a substance by 1 K

Defining property of SHM

Acceleration is proportional to negative displacement (proportional to displacement and restorative)

What type of wave is sound?

Longitudinal

Resistance

Ratio of potential difference across a device to current through the device (R=V/I) (NOT a gradient!)

Emissivity

Ratio: Power radiated by an object per unit area / Power radiated per unit area by a black body at the same temperature

Potential Difference

Work done per unit charge in moving a charge between 2 points in an E field (1 V = 1 J/C)!

Velocity vs. time graph - how do you find acceleration?

Gradient (slope of the tangent line)

Velocity vs. time graph - how do you find displacement?

Area under the curve

Moderator

Slows neutrons in a fission reactor to allow further reactions to take place (water is a common moderator)

Heat

Thermal energy (Q), measured in Joules - can be transferred between two objects in thermal contact until they reach thermal equilibrium

Most used energy source overall

Oil

Specific energy

Energy per unit mass for a fuel source

Mass defect

Difference between the mass of a nucleus and the total mass of its individual nucleons

Efficiency of a coal power plant

30-35%

How do you place an ammeter in a circuit, and what is its resistance?

In series, 0

Transverse wave

Particles oscillate perpendicular to the direction of propagation of the wave

Free fall

Gravitational force is the only force acting on an object

Renewable energy

Rate of consumption < rate of production

Acceleration

Rate of change of velocity (a = Δv/Δt, AKA dv/dt) (definitely NOT v/t)

Energy density

Energy per unit volume for a fuel source

Energy density

Energy per unit volume for a fuel source

Electric field strength

Electric force per unit charge at a point in space, on a small test charge

What provided evidence for atomic energy levels?

Emission / absorption spectra

What's an alpha particle?

Helium nucleus (2 protons, 2 neutrons)

State Newton's Second Law

The resultant (net) force on an object is equal to its rate of change of momentum (F \= ∆p/∆t)

State the law of conservation of momentum

Momentum in a system does not change unless a net external force acts on the system

Albedo

Fraction / percent of incoming radiation that is reflected back into space

Define 1 electron volt, and state its value

The energy gained by an electron moving through a potential difference of 1 volt (1 eV \= 1.6 x 10^-19 J)

Gravitational field strength

Gravitational force per unit mass at a point in space on a small test mass

How do you place a voltmeter in a circuit, and what is its resistance?

In parallel, infinite resistance

What type of wave is light?

EM wave/Transverse wave (electromagnetic wave)

Charge of an alpha particle

+2e

Elastic collision

Momentum AND kinetic energy are conserved

Most used energy source in electrical energy generation

Coal

Unified atomic mass unit (u)

1/12 the rest mass of carbon-12 in its ground state

Rank the 3 fossil fuels in order of increasing efficiency

Coal < Oil < Natural gas

Control rods

Moveable rods that absorb neutrons to control the rate of the fission reaction in a nuclear reactor

When do you get constructive interference?

When 2 waves meet in phase at a point in space / When the path difference is n*(wavelength)

emf of a battery

The work done by the battery per unit charge in powering the entire circuit, including the energy dissipated as heat inside of the battery due to its internal resistance. (Stands for electromotive force, but it's not a force!!)

Polarization

Direction of oscillation of the E field in an EM wave

State Newton's Third Law

When two bodies A and B interact, the force that A exerts on B is equal and opposite to the force that B exerts on A

Half-life

Average time taken for half a parent nuclei to decay

Systematic error

Error that skews all data points in the same direction away from the "true" value

Outline the process of the greenhouse effect

\-Solar radiation (mainly visible & UV) passes through the atmosphere

\-Radiation is absorbed by the Earth

\-Earth radiates its own EM radiation as a black body, mainly as infrared

\-Some IR radiation is absorbed by greenhouse gases due to RESONANCE

\-GHG re-radiates IR radiation randomly / in all directions

\-Some IR radiation directed back towards the surface of Earth, further heating the planet

List the regions of the EM spectrum, low to high frequency

Radio, microwave, infrared, visible, ultraviolet, X-ray, gamma

Order of magnitude of the wavelength of visible light

10^-7 m

What macroscopic property of a substance is related to potential energy?

Phase

Define the temperature of a substance

Measure of the average kinetic energy of its molecules

When do you get destructive interference?

2 waves arrive at a point in space out of phase / the path difference is (n + 1/2)*(wavelength)

Photovoltaic cells

Convert light to electrical energy

Optically active substance

Substance (e.g. sugar water) that rotates the plane of polarization of incident polarized light

How do you calculate average velocity?

Total displacement / Total time

Beta particle

Electron (beta minus) or positron (beta plus), charge of -e or +e

Current

Rate of flow of electrical charge, measured in coulombs per second. I \= Δq/Δt

What macroscopic property of a substance is related to kinetic energy?

Temperature

Impulse

The change in momentum of an object (Δp). Equal to the product of net force and duration of collision (Δp \= FΔt)

State Newton's 1st Law

An object will maintain a state of translational equilibrium unless acted upon by a net external force.

Longitudinal wave

Particles oscillate parallel to the direction of propagation

Main use of pumped hydroelectric systems

Store energy for later use (uses gravitational potential energy)

How can you graphically determine impulse?

Area under the curve for a force vs. time graph

Solar constant

Amount of solar energy incident per second on an area of 1 m^2 above Earth's atmosphere that is at right angles to the Sun's rays (~1360 W/(m^2) [in the data booklet!])

Glaciers role in Earth's climate

Reflect incoming light, increase albedo

List the main greenhouse gases

Water vapor, carbon dioxide, methane, nitrous oxide

Properties of a standing wave

\-Does not transfer energy

\-Has nodes (points of 0 amplitude)

\-All points have different amplitudes

\-Two points are either completely in phase (0°) or completely out of phase (180°)

Define random error

Error that causes measurements to skew randomly about the "true" value

Efficiency of an oil power plant

35-40%

Solar constant is ~1400 W/(m^2). Why is the average solar intensity on Earth's surface much less? ~350 W/(m^2)

Energy spreads over the sphere of Earth's surface. Solar constant is expressed in terms of circular cross section... π(r^2) vs. 4π(r^2)

When can you use P \= Fv?

Constant speed against a resistive force

Frequency of the first harmonic of a string fixed at both ends

v/2L

Assumption of LUG

Masses act as point masses

Fission

Heavy nucleus splits into 2 lighter nuclei, releases energy (right side of binding energy curve)

When is momentum NOT conserved in a collision?

When a net external force acts on the system

Efficiency of a natural gas power plant

~45%

Limitation of suvat

Constant acceleration

Object is sliding down a ramp. Normal force is equal in magnitude to what other force?

Component of weight perpendicular to the ramp (=mgcosθ)

Ohm's law

Current flowing through a conductor is proportional to the potential difference, providing the temperature remains constant / Resistance of a conductor is constant, providing the temperature remains constant

Order of magnitude: Size of a nucleus

10^-15 m

Frequency of the first harmonic of a pipe open at both ends

v/2L

7 base units

kilogram, meter, second, ampere, mole, kelvin, candela

Inelastic collision

Momentum is conserved, but kinetic energy is not

Centrifugal force

NO SUCH THING!

Difference between amplitude & displacement

Amplitude is the maximum displacement of an oscillating particle

Thermistor

Resistor whose resistance depends on temperature (usually decreases with increasing temperature)

Wind equation limitation / assumption

Equation gives the available power from a cross section of wind - all the wind can't be captured (or the wind would stop!) Betz limit gives maximum theoretical efficiency of a wind turbine, ~59%

Why do greenhouse gases heat the Earth? (property responsible)

RESONANCE allows them to absorb and re-radiate IR radiation

Frequency of the first harmonic for a pipe closed at one end (open at the other)

v/4L

Fusion

2 light nuceli combine to form a heavier nucleus, releasing energy (left side of binding energy curve)

An object slides down a ramp at constant speed. The frictional force is equal in magnitude to…

the component of weight parallel to the ramp (\=mgsinθ)

LDR

Light dependent resistor. Resistance increases with increasing intensity

Besides using a polarizer, how can light become polarized?

Reflect off a surface (e.g. water)

Which experiment provided evidence for the nucleus?

Geiger-Marsden experiment (AKA Rutherford-Geiger-Marsden)

Right hand rule #1

\-Pointer finger = v (or I)

\-Middle finger = B

\-Thumb = F on a + charge

Right hand rule #2 (both ways)

\-Point thumb in direction of current, fingers curl to show direction of circular B field

\-Curl fingers in direction of circular current (for a coil) to get thumb as direction of B field inside coil

An object in UCM moves with constant speed, why is it accelerating?

The direction of v is constantly changing, so velocity is changing, therefore it is accelerating.