Physics Exam 2 definitions

Potential Energy

The energy stored in the bonds between the particles

Thermal Expansion

The general increase in the volume of a material as its temperature increased.

Heat

A form of energy that transfers from a hotter region into a cooler region that is measured in joules.

Temperature

The average kinetic energy of a body measured in Celsius or Kelvin

Internal Energy

Total energy, kinetic and potential, that is contained within each atom/molecule of a substance.

Absolute Zero

Lowest possible temperature when molecular motion stops

Heat Capacity

The heat energy needed to raise the temperature of an object by 1K

Specific Heat Capacity

The heat energy needed to raise the temperature of 1kg of the substance by 1K

Latent Heat of Fusion

Heat energy absorbed by a solid when it melts

Latent Heat of Evaporation

Heat absorbed by a liquid when it evaporates

Conduction

Transfer of thermal energy from warmer matter to cooler matter by direct contact. Particles vibrate and bump into neighbouring particles, transferring energy at the contact. Requires particles.

Convection

Transfer of thermal energy through movement of particles in liquids and gasses. Hotter fluid rises and cooler fluid sinks. Requires particles.

Radiation

Transfer of energy without affecting the median through which it travels. Does not require particles.

Thermal Equilibrium

Is obtained when touching objects within a system reach the same temperature which means there is no net heat flow

Strong Nuclear Force

Force in nucleus that is strong enough to overcome the electrostatic repulsion of the protons and binds the nucleus together

Half-Life

The time taken for the mass of a specified isotope to decay to half its original value

Radioactivity

Amount of ionising radiation released by a material. (Bq)

Exposure

Amount of radiation travelling through the air. (C/kg)

Absorbed Dose

Amount of radiation absorbed by an object or person (Gy)

Dose Equivalent

Combines the amount of radiation absorbed and the medical effects of that type of radiation. (Sv)

Electron Volt

Is a unit of energy that is equal to the amount of joules one electron has in a voltage of 1 volt

Atomic Mass Unit (1 u)

is equal to one-twelfth of the mass of the most abundant form of the atom-carbon-12

Binding Energy

The energy required to separate a nucleus into its individual protons and neutrons without providing them with kinetic energy

Mass Defect

The nucleus of each atom has a mass lower than expected from adding the masses of its neutrons and protons because it has been converted into energy

Mass- Energy Equivalence

The mass defect is converted into energy by Einstein's equation E=m c^2

Fission

Splitting a heavy nucleus into two nuclei with smaller mass number

Fusion

Combining two light nuclei to form a heavier, more stable nucleus

Chain Reaction

A chain reaction occurs in a critical mass and refers to a process in which neutrons released in fission produce an additional fission in at least one further nucleus.

Sub-critical mass

The sphere of fissile material is too small to allow the chain reaction process to become self-sustaining as neutrons can too easily escape

Critical mass

When the sphere of fissile material is big enough to stop too many neutrons escaping and thus sustaining a chain reaction

Coulomb barrier

energy barrier due to electrostatic interaction that two nuclei need to overcome so they can get close enough to undergo a nuclear reaction and fuse together

Electrostatic induction

a redistribution of electric charge in an object, caused by the influence of nearby charges.

EMF=Electromotive Force

The maximum source a power source can have and isn't actually a force(energy per charge)

Static Electricity

Occurs when there is a build up of electric charge on a surface and the charged particles are transferred from one body to another.

Electric current

The synchronized movement of charge(electrons) in one direction

Conventional current

Benjamin Franklin's kite experiment made scientists think that positive charges carried current

Electron Flow Model

Electrons flow from the negative terminal to the positive terminal

Mains Voltage in Australia

230V, 50Hz

Electrical Power

amount of work done by an electric current per unit time in Watts

Rheostat or variable resistor

A resistor that produces variable amounts of resistance e.g use for volume or light dimming

AC=Alternating current

The type of current from mains power where the current changes continuously and the voltage is also changing. More efficient to generate and transmit

DC=direct current

The type of current that comes from the batteries, where the current flows in one direction and the voltage stays constant

Effective Value

An equivalent DC value which states how many volts or amps of DC that AC is equal to in terms of its ability to produce the same power

RMS= Root-Mean-Squared

Mathematical way to define the effective value of an AC wave.

Transformer

device that steps ups or steps down AC voltage

Active Wire(brown/red)

Carries current to the power point

Neutral Wire(blue/black)

carries current away from power point

Earth Wire (Green/yellow)

connects power point to the earth or ground as a safety feature

Short Circuit/ electrical fault

When current travels along an unintended path because it is shorter and has low resistance

Fuses

Are designed to stop damage resulting from short circuits by having a metal with a low meting point that melts and stops the current if there it too much current.

RCD=Residual-Current Device

Measure that current in live wire is the same as current in neutral wire and if it isn't (because someone has touched a live wire) it turns it off so damage will be less severe

Thermistors

heat sensitive resistors that has the resistance decrease when temperature increases. E.g. Used in thermostats in air cons

Momentum

the strength or force that allows something to continue or grow stronger/faster as time passes.

Impulse

the change in momentum because velocity has changed

Weight

the force on an object due to earth pulling the object down

Work

A measure of energy transfer that occurs when an object is moved over a distance by an external force

Mechanical Energy

Is the energy an object gains when work is done on it

Power

Rate of doing work

Friction

Force that resists the relative motion of objects sliding against each other

Wave

A repeating and periodic disturbance that travels through a medium from one location to another

Pulse

A single disturbance moving through a medium from one location to another

Electromagnetic

A wave that is capable of transmitting energy without a medium

Mechanical

A wave that requires a medium in order to transport energy from one location to another

Medium

A substance or material that carries the wave

Transverse wave

a wave in which particles of the medium move in a direction perpendicular to the direction the waves move

Longitude

a wave in which particles of the medium move in a direction parallel to the direction the wave moves

Compression

A point on medium through which a longitude wave is travelling that has the maximum density/pressure

Rarefaction

Point on medium through which a longitudinal wave is travelling that has the minimum density/pressure

Elasticity

tendency of a substance to maintain its shape/ return to its original shape

Doppler effect

Change in frequency and wavelength of a wave caused by movement of the source relative to the receiver of the source.

Intensity level

Comparison of the sound energy of a noise with that of one just detectable at the threshold of hearing

Law of Reflection

the angle on incidence is equal to the angle of reflection

Reverberation

perceived when the reflected sound wave reaches your ear in less than 0.1 second after the original sound wave .

Echo

perceived when sound wave is reflected and reaches your ear in more than 0.1 seconds after the original wave

Beats

periodic and repeating fluctuations heard in the intensity of a sound when two sound waves of similar frequency interfere with one another

Lateral inversion

Image in a plane mirror appearing to be reversed sideways

Virtual Image

image where the light rays do not actually meet, but appear to meet at a point inside/behind the mirror

Refraction

the bending of light rays due to the different speeds

Critical Angle

Angle of incidence that results in a refracted ray that runs along the boundary

Total Internal Reflection

Occurs when the light ray is completely reflected internally due to the angle of incidence being greater than the critical angle and no light being refracted.

Diffraction

Interference/bending of waves around obstacles

Phase

refers t the stage of vibration that a particle has reached in its cycle of motion. It can be measured in wavelengths or degrees.

In Phase

Waves that have the same frequencies and are in line , 0 degrees or 360 degrees apart

Out of Phase

Not the same frequency and aren't 0/360 degrees apart

Superposition principle

When two or more waves overlap, the resulting disturbance is the sum of the individual disturbances

Constructive Interference

When both have positive/ both have negative amplitude so add amplitudes together to make a bigger amplitude

Destructive Interference

When both don't have the same positive amplitude or same negative amplitude the amplitudes subtract from each other

Natural Frequency

The frequency at which a system tends to oscillate in the absence of any driving force.

Resonance

Achieved when energy is added to a system at the same frequency as its natural frequency which results in maximum amplitude

Standing wave

waves with equal amplitude, wavelength and frequency travelling in opposite direction in same medium

Newton's first law

1. An object in moving in a particular direction will continue moving at the same speed and direction until another force is enacted upon it.
A stationary object will remain stationary until another force in acted on it.
Also known as law of inertia

Newton's second law

Force= mass x acceleration
Force is directly proportional to mass and accelerationà if mass stays constant, an increased acceleration causes an increased force. If acceleration stays constant, an increased mass causes an increased force
Mass and acceleration are indirectly proportionalà when force stays constant an increased mass means a decreased acceleration and vice versa

Newton's third law

For every reaction there is an equal and opposite reaction

If all arrows are the same and add to zero...

object is stationary, at constant velocity

Weight depends on what force?

Normal force

What happens when elevator goes up

F=ma
Your mass stays constant.
The elevator accelerates upwards.
To counter gravity that stays constant, the normal force has to push up more. So the normal force increases.
The increased normal force makes you heavier.

What happens when elevator goes down

Your mass stays constant.
The elevator accelerates downwards.
Since gravity stays the same, this means that the normal force must not be pushing back as hard so you can go down. So the normal force decreases.
The decreased normal force makes you lighter.

momentum

The strength or force that allows something to continue or grow stronger/faster as time passes.

Formula for momentum

P=mv

Impulse

the change in momentum because velocity has changed