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