All Physics Formulas for O levels Physics by Ethan Wu

[Pages:6]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

E-energy t-time

2 Formulas for Transformer

Vs Vp

=

Ns Np

VpIp=VsIs

Vs output voltage Vp input voltage Ns number of turns in secondary coil Np number of turns in primary coil Is current in secondary coil Ip current in primary coil

Efficiency of a transformer =

output power input power

? 100%

Joule heating/ Power Loss due to heat P = I2R

Compiled by Ethan Wu Ying Tang

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