Equations

Biology

7 Equations

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Magnification

Magnification=

size of image ÷ size of real object

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SA:V

Cube- 3cm

SA: (3*3)6= 54

V: 3*3*3= 27

54:27

2:1

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No. of bacteria in a population

e.g. mean time for division= 30 mins

How many after 8hrs?

1. 2 times per hour

16 times every 8 hrs

2. bacteria at end= bacteria at start x 2 to the power of number of division

=1 x 2 to the power of 16

= 65536

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Effect of disinfectants & antibiotics on bacterial

Use area of a circle

Biggest one is the most effective

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Frequency density

frequency density=

frequency ÷ class width

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Plant population size

estimated population size=

mean population per unit ÷ total area

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Units

1km= 1000m

1m= 100cm

1cm= 10mm

1mm= 1000 micromtres

1 micrometre= 1000 nanometres

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Chemistry

8 equations

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Number of neutrons

number of neutrons=

mass number - atomic number

(top - bottom)

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Moles

number of moles=

mass (g) ÷ RAM

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Percentage yield

percentage yield=

mass of product produced ÷ max. mass of product possible

(actual ÷ theoretical)

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% of atom economy

% of atom economy=

RAM of desired product ÷ sum of RAM of reactants

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Concentration

concentration (moles/dm )=

number of moles ÷ volume (cm )

1000cm= 1dm

the number of moles is the same in a titration

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No. of moles of a gas

no. of moles of a gas=

volume ÷ 24dm

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Mean in an experiment

mean rate=

mass of reactants use up (g) ÷ time (s)

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Unknown mass

unknown mass =

known mass ÷ total Mr of known substance × total Mr of unknown substance

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Physics

32 equations

(c)= compulsory

(o)= optional

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Work done

work done (J)= (c)

force applied (N) x distance moved along line (m)

W =F x s

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Gravitational Potential Energy

change in gpe (J)= (c)

mass (kg) x GFS (N/kg) x change in height (m)

GPE= m x g x h

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Kinetic energy

kinetic energy (J)= (c)

0.5 x mass (kg) x speed (m/s )

KE= 0.5 x m x v

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Efficiency

efficiency (%)= (c)

useful power/energy (J) ÷ total power/energy (J)

E= U ÷ T

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Power

power (W)= (c)

energy (J) ÷ time taken (s)

P= E ÷ t

current (A) x resistance (ohms)

P= I x R

current (A) x potential difference (V)

P= I x V

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Charge flow

charge flow (C)= (c)

current (A) x time taken (s)

Q= I x t

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Potential difference

potential difference (V)= (c)

energy (J)/ power (W) ÷ charge (C)

V= E/P ÷ Q

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Density

density (kg/m )= (c)

mass (kg) ÷ volume (m )

DE= m ÷ v

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Moment

moment (Nm)= (c)

force (N) x distance from pivot (m)

M= F x d

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Acceleration

acceleration (m/s )= (c)

[final velocity (m/s) - inital velocity (m/s)] ÷ time (s)

a= [v-u] ÷ t

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Weight

weight (N)= (c)

mass (kg) x GFS (N/kg)

W= m x g

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Resultant force

resultant force (N)= (c)

mass (kg) x acceleration (m/s )

F= m x a

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Momentum

momentum (kg m/s)= (c)

mass (kg) x velocity (m/s)

Mo= m x v

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Force

force (N)= (c)

spring constant (N/m) x extension (m)

F= K x e

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Pressure

pressure (Pa)= (c)

force (N) ÷ area (m )

p= F ÷ A

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Pressure (liquid)

pressure (Pa)= (c)

height (m) x density (kg/m ) x GFS (N/kg)

p= h x de x g

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Wave speed

wave speed (m/s)= (c)

frequency (Hz) x wave length (m)

v= f x wl

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Elastic potential energy

elastic potential energy (J)= (o)

0.5 x spring constant (N/m) x extension (m )

EPE= 0.5 x k x e

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Specific heat capacity

specific heat capacity (J/kg C)= (o)

energy (J) ÷ [mass (kg) x temperature change (C)]

C= E ÷ [m x temp]

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Specific latent heat of fusion/vapourisation

specific latent heat of fusion/vapourisation (J/kg)= (o)

energy (J) ÷ mass (kg)

L= E ÷ m

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Constant

constant= (o)

pressure (Pa) x volume (m )

constant= p x vo

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Kinematic

v = (o)

u + [2 x a x s]

v= final speed

u= intial speed

a= acceleration

s= distance travelled

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Magnetic flux density

force (N)= (o)

magnetic flux density (T) x current (A) x length (m)

F= B x I x le

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Transformer

p.d across pri coil ÷ p.d across seco coil = no. of turns on pri coil ÷ no. of turns on seco coil (o)

Vp ÷ Vs = Np ÷ Ns

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Transformer efficiency

primary p.d x primary current = secondary p.d x secondary current (o)

Vp x Ip = Vs x Is

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Resistance

resistance (ohms)=

potential difference (V) ÷ charge (C)

R= V ÷ Q

Resistance of resistors=

R1 + R2 + .....

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Principle of moments

sum of all clockwise moments = sum of all anticlockwise moments

W1 x D1 = W2 x D2

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Stopping distance

stopping distance=

thinking distance + braking distance

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