All Physics Formulas for O levels Physics by Ethan Wu
All Physics Formulas for O levels Physics by Ethan Wu
Celsius to Kelvin ?C =K - 273.15
Factor 1012 109 106 103 10-1 10-2 10-3 10-6 10-9 10-12
Prefix Prefix TeraGigaMegaKiloDeciCentiMilliMicroNanoPico-
Symbol T G M k d c m ? n p
Formula for period of pendulum
L T=2g
T is period L is length G is acceleration due to gravity
Speed is the distance moved per unit Speed = distance / time (assuming constant seed)
total distance average speed= total time Velocity is the rate of change of displacement Acceleration is the rate of change of velocity Acceleration = (final velocity ? initial velocity)/time
Newton's 2nd Law F (force)=m (mass) ? a (acceleration)
Weight W (weight)=m (mass)? g (gravitational field strength)
Gravitational field strength on earth = 10N/kg On moon, 1/6 that of earth
Density mass
Density= volume
Compiled by Ethan Wu Ying Tang
Moment moment=force ? perpendicular distance from line of action of force to the pivot
Principle of Moment If in equilibrium, total anticlockwise moment = total clockwise moment
Efficiency useful energy output Efficiency= total energy input ?100%
Work Done Work done=force ? distance moved (must be same direction as force)
Kinetic Energy
Kinetic
Energy=
1 2
mv2
Gravitational Potential Energy Gravitational Potential Energy=mgh
m = mass v = velocity h = height g = acceleration due to gravity
Power is defined as rate of work done or rate of energy conversion. (SI unit watt W)
work done or energy converted
Power=
time
Power =force ? velocity
Pressure Force
Pressure= Area
Pressure=hg h = height
= density of liquid g = acceleration due to gravity Density of mercury 13600 kg/m3 Density of water 1000 kg/m3
Compiled by Ethan Wu Ying Tang
Thermometer
=
- 0 100 - 0
? 100
= unknown temperature
= physical property at temperature 0= physical property at temperature at 0 100 = physical property at temperature at 100
Thermocouple
= emf (in V) = temperature difference between the junction
Kinetic Model of Matter
If volume fixed, pressure temperature
If
temperature
fixed,
pressure
1 volume
(Boyle's
law)
If pressure fixed, volume temperature
Heat Capacity Q=C
Specific Heat Capacity Q=mc
Q ? thermal energy required (in J) C ? heat capacity ( in JK-1 or J?C) c ? specific heat capacity (Jkg-1K-1)
? temperature change m ? mass of substance (in kg)
Latent heat of fusion
Lf=lf?m Lf ? latent heat of fusion (in J) Lf ? specific latent heat of fusion (in J kg-1)
m ? mass of substance (in kg)
Latent heat of vaporization
Lv=lv?m Lv ? latent heat of vaporization (in J) Lv ? specific latent heat of vaporization (in J kg-1)
m ? mass of substance (in kg)
Compiled by Ethan Wu Ying Tang
Law of reflection i = r
i = angle of incidence, r = angle of reflection
Law of refraction (Snell's Law) sin sin =
C N= V N ? refractive index of medium C ? speed of light in vacuum V ? speed of light in medium
real depth N = apparent depth
Critical angle 1
sin =
Speed of light = 3 x 108 m/s
The period T of a wave is the time taken to produce one complete wave. (SI unit second s) The frequency f of a wave is the number of complete waves produced per second. (SI unit hertz Hz) Wave speed is the distance travelled by a wave per second. (SI unit meter per second) A wavefront is an imaginary line on a wave that joins all adjacent points that are in phase.
v = f
T=1/f
Sound Amplitude proportionate to loudness
Frequency proportionate to pitch Speed of sound in air 340m/s
Current
= I = current (A) Q = charge (C)
T = time (s)
Charge carried by 1 electron/ proton = 1.6 x 10-19 coulombs
Compiled by Ethan Wu Ying Tang
Electromotive force/potential difference
= = e.m.f (V)
W= work done (J)
Q = amount of charge (C)
Resistance
= R = resistance of component in ohm ()
V = potential difference across component (V)
I= current flowing through the component (A)
Ohm's Law states that the current passing through a metallic conductor is directly proportional to the potential difference across it, provided that physical conditions remain constant.
= =
Resistivity
= R-resistance (in ) ? Resistivity (in m) constant value, depends on type of substance
l- Length (m) A- Cross sectional area (in m2)
For a series circuit The total resistance is the sum of individual resistances added up For a parallel circuit The reciprocal of the effective resistance of resistors in parallel is equal to sum of reciprocal of all the individual resistances.
1 11
1
= 1 + 2 + +
A potential divider is a line of resistors connected in series. It is used to provide a fraction of the voltage
of a source to another part of the circuit
Vout
=
R2 R1+R2
?V
P=VI
=I2R=
V2 R
E=VIt
P-power (watt W)
V-voltage
I-current
Compiled by Ethan Wu Ying Tang
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