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Pre Q Physics

what is a alpha particle

particles emitted from nucleus large atoms

2 protons, 2 neutrons

charge +2

am 4

move relatively slow

helium atom

what is a beta particle

emmited from nucleus of atom
single electron leaving

moves faster

high energy electron

charge -1

almost no mass

what is a Gamma particle

electromagnetic wave released from nucleas
moves at speed of light

Ionisation

turning a nuetral atom into an ion
atom becomes charged


alpha - best

gamma - worst

Half life

the time is takes for half the number of radioactive particles on a sample to decay particles

when radioactive sources give out radiation, they decay


the number of radioactive particles decreases

Nuclear fission

the splitting of atomic nuclei and is used in nuclear reactors as heat energy.
absorbs a neutron to split

chain reactions

Nuclear fusion

the joining of two atomic nuclei to form a larger one

describe a elemets characteristics

Mass number (p+n) Nucleons
- A

X

- Z

atomic number, no. of electrons or protons

Isotope

Same atomic number
diff mass number

Accurate

close to true value
more repeats give a more accurate

Presice

little variation between readings
highly repeatable

Graphing
gradient?

gradient= y1- y2
-----------

x1-x2


Rise distance

------- = -------------- = speed

run time

Scalar & Vector quantities

Scalar = have only size
e.g distance, speed


Vector = size and direction

e.g displacement, velocity

acceleration

A = change in velocity
----------------------------

time


initial velocity - U


change in V V - U

------------------ = ----------------

time time


V = U + AT

Graphs of motion

Distance time
diagonal line - constant speed

accel 0

gradient - speed

straight line - stationary


Speed time

diagonal line - constant acceleration

straight line - constant speed

Speed,Velocity,Acceleration

Speed
avs = distance moved

time taken

Velocity

V = dm in stated direction

time taken

Acceleration

acc = change in V

time taken for change

SUVAT equations

V = u + at
S = ut + 1 a + 2

_

2

V2 = U2 + 2as


S = 1 ( u + v )

-

2

SUVAT

S - displacement
U - initial velocity

V - final velocity

A - constant value of the acceleration

T - time

Hookes law

F = KX
f - force applied

x - extension or compression

k - force constant, the force need to produce a unit extension, k tells us the stiffness of the spring.


The amount a spring stretches is proportional to the force applied

Circular Motion

Centripical Force - fc
Centripical acceleration - ac

v 2

ac = ----

r


F = mv2

r


v = d = 2πr

t t

Moment(Torque)

The Moment describes the turning effect of force around a fixed pivot


Moment = Force x Distance

Nm = N x M


Torque = F x perpendicular distance



Work = F x linear distance

Momentum

P
M = mass x Velocity


p = mv


p - kg ms-1

m - kg

v - ms-1


Momentum is a vector quantity

direction same as velocity


Force - change in momentum

change in time

Impulse

change im momentum

( F x change in time) = change( mv)

Newtons Laws

1st - object in motion will remain in motion unless acted apon by another force

2nd - the rate of change in momentum is equal to the force applied


3rd - every reaction has an equal or opposite reaction

work, energy, power

energy, ability to do work - Joules, J

power, ability to produce work in a short span of time


p= w

t


angle involved - w = f cos q

q - angle


kinetic energy Ek= 0.5mv2


gravitational poten energy Ep= mgh

Unit conversion

micro - x10 -6
milli - x10 -3

centi - x10 -2


mega - x10xp6

kilo - x10xp3

Density

the amount of mass in a certain space, measured in g/cm3

D = M/V


E=M/V - g/cm3

Pressure

solids - P = F/A

liquids - P = heg


h - height

e - density

g - gravity, 9.81 Nkg


unit - Pascals, Pa

States of matter

solid to gas - add energy
gas to solid - remove energy


Thermal physics


speed of light \ speed of sound

/


solid to gas - Sublemation

Temperature

the average speed of the particles

Thermocouple

- diff metals are twisted together
- metals are heated, small current produced

- ↑ current, ↑ temp

Bimetallic strips

relies on fact that diff metals expand at diff rates as they warm up

by bonding two metals together you can make a simple electric controller that can withstand fairly high temps

Recording thermometer

records temp over long periods of time

pen on bimetallic strip records temp on rotating drum

Infrared thermograms

A camera like device that measures
the amount of radiant energy given off by an object

Boyles law

Pressure is Inversely proportional to volume

P x 1/V

V = 1/P

for a fixed mass of gas the pressure is inversely proportional to the volume at a constant temperature


PV a constant


P1 x V1 = P2 x V2


1 - initial

2 - final


Charle Law( The pressure Law) - the volume or pressure of a final mass of gas, is proportional to the absolute temperature

Combined gas equation

P1V1 = P2V2
T1 T2


T - degrees Kelvin (+273 to convert)

Heat capacity

the amount of energy needed to raise the temp of 1kg of a substance by 1c

E = M x C x change in T


E - energy transferred

M - mass

C - specific heat capacity

T - Change in temp, Ft - It



↑ volume, ↑ heat capacity


small volumes - faster heating and cooling


↑ specific heat capacity gets hotter slower


↓ shc gets hotter faster

Specific heat capacity

C = E / M x chan T = J/kg

Specific Latent Heat

is the heat required to melt a solid OR evaporate a liquid

E = mass x SPLH


Types:


Latent heat fusion = energy required to melt a solid


Latent heat of vaporisation = energy required to turn a liquid from a gas

Thermal expansion

change in size (length, area, volume) of a material in response to a change in temp

- particles vibrate faster with heat and it pushes the particles further apart hence increasing the size of the object


Solids - usually retain thier shape so are best described by a linear coefficient of thermal expansion


Liquids - as the bonds between particles in a liq are not stiff as those in solids, liquids expand more for a given temp rise


Gases - there are no bonds between particles in a gas and so small change in temp can result in a larger change in volume

Waves

they all carry energy from one place to another

they involve some sort of oscillation

Transverse Waves

Wavelength = lamder, speed of the wave

amplitude = volume, how much energy been given

↓

the maximum distance a point moves from its rest position


Frequency - number of waves passing per second , Hertz, Hz


V = F x Lamda


f - frequency

Longitudinal Waves

oscillation and propagation are parallel to each other

Diffraction

when waves pass through gaps

gap is equal to wavelength, if the gap is too large most of the energy gets through, but most of waves pass straight through so diffraction is ineffective

Interference

A pattern of bands where waves reinforce each other or cancel each other out

- can be used to test if something is a wave or a particle

water wave diffraction

- waves slow down in shallow water
- straight lines are called wave fronts

- the frequency of the wave doesn't change

the wavelength is decreasing

refraction through a glass block

Snells law

n1sin©1 = n2sin©2


© - angle of incident

n - refractive index

Critical angle

when light is passing from some medium, glass or water, with ri into water - Sin C = 1/n

Sin C = nr/n1


nr - refractive index of medium light is passing into


n1 - refractive index of medium light is in

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