# Physics O Levels Formula Sheet

1) **Speed**

= distance / time

s = d / t (in symbol)

unit = km/h , m/s , cm/s

2) **Acceleration**

= change in velocity / time

a = v - u / t (v = final speed, u = Initial Speed, t = Time)

unit = m/s^{2}

3) **Average Speed**

= total distance travelled / total time taken

s = d / t

unit = km/h, m/s, cm/s

4) **Velocity**

= displacement / time

v = dis / t

unit = m/s, km/h, cm/s

5) **Force**

= mass x acceleration

F = ma

unit = N (newton)

6) **Weight**

= mass x gravitational field strength

W = mg

unit = N (newton)

7) **Density**

= mass / volume

ρ = m / v

unit = g/cm^{3}, kg/m^{3}

8) **Moment**

= Force x perpendicular distance

m = F x d

unit = Nm (newton meter)

9) **Principal Of Moment**

sum of clockwise moment = sum of anticlockwise moment

F x d = F x d

10) **Extension**

= loaded length - unloaded length

x = L - l_{0}

unit = mm , cm

11) **Pressure**

= Force / Area

p = F / A

unit = Pa (Pascal) , N/m^{2}

12) **Liquid Pressure**

= density x gravity x height of the liquid

P = p g h

unit = Pa, N/m^{2}

13)** Pressure volume relationship of a gas**

initial pressure x initial volume = final pressure x final volume

P_{1} V_{1} = P_{2} V_{2}

14) **Pressure transmission**

initial force / initial area = final force / final area

F_{1} / A_{1} = F_{2} / A_{2}

15)** Kinetic Energy**

= 1/2 x mass x (velocity)^{2}_{}

KE = 1/2 mv^{2}

Unit = J (Joule)

16) **Potential Energy**

= mass x gravity x height

PE = mgh

unit = J

17) **Work done**

= Force x distance (travelled in the direction of force)

W = F x d

unit = J

18) **Power**

= work done or energy supplied/ time taken

p = W / t

unit = W (Watt) , KW (kilo watt)

19) **Efficiency**

= energy output / energy input x 100

Or

= power output / power input x 100

Unit = %

20) **Heat Capacity**

= thermal energy / change in temperature

C = E / Δ T

unit = J/^{0}C^{}

21) **Specific heat capacity**

= thermal energy / mass x change in temperature

c = E / m ΔT

unit = J/kg °C , J/g °C

22) **Specific latent heat**

= thermal energy / mass

l = E / m

unit = J/kg , J/g

23)** Wave Equation**

speed of wave = frequency x wavelength

v = f λ (λ is wavelength)

24) **Frequency**

= 1 oscillation / time taken

f = 1 / t

unit = Hz

25) **Electrical Power**

= Voltage x Current

Or

= (voltage)^{2} / Resistance

Or

= (current)^{2} x resistance

p = VI , p = V

^{2}/R, p = I

^{2}/R

__unit = W (watt) , KW (kilo watt)__

26) **Refractive index**

__n= sin i / sin r (when going from rarer to denser medium)__

__ Or__

__n= sin r / sin i (when going from denser to rarer medium)__

__ Or__

__n = 1 / sin c (c is the critical angle)__

27) **Resistance**

__= Voltage / Current__

__R = V / I__

__unit = Ω (ohm)__

28) **Current**

__= charge / time__

__I = Q / t__

__unit = A (ampere) , mA __

29) **Electromotive force**

__= work done / charge__

__e.m.f.= E / Q__

__unit = V__

30) **Potential difference**

__= work done / charge__

__p.d = E / Q__

__unit = V__

31) **Resistance is series**

R= R_{1} + R_{2} + R_{3} …

unit = Ω

32) **Resistance in parallel**

1/R = 1/R_{1} + 1/R_{2} + 1/R_{3} . . .

Or

R = R_{1} x R_{2} / R_{1} + R_{2}

unit = Ω

33) **Temperature**

θ = X_{θ} - X_{0} / X_{100} - X_{0} x 100 (θ is the unknown temperature and X is the physical property of the thermometric substance)

34) **Electrical energy**

= voltage x current x time

Or

= power x time

E = VI , E = Pt

unit = J, KWh

35) **Cost of electricity**

= energy in KWh x cost per unit

36) **Hook's Law**

= F_{1} / x_{1} = F_{2} / x_{2} (F is the force and x is the extension)

- You can rearrange any of the equation according to the question. These are important formulas and other formulas can be made by changing the subject of the equation.