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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