Equations Flashcards
Average Orbital Speed
Avg Orbital Speed = 2 x pi x radius of orbit / orbital period
Age of Universe
Distance / speed
1/Hubble Constant
14.4 billion years
Hubble Constant
Hubble constant = speed of galaxy/distance of galaxy from earth
H0= v/d
Alpha decay
Number of protons and neutrons decrease
238/92U=234/90Th + 4/2a
Beta Decay
Number of protons increase by 1
14/6C=14/7N + 0/-1B
Nuclear Fission
Splitting large ,unstable nucleus
235/92U + 1/0n = 91/36Kr + 143/56Ba + 2 1/0n + 0/0y
Nuclear Fusion
Joining of small nuclei
2/1H + 1/1H = 3/2He + 0/0Y
Gamma decay
No change
A/ZN = A/ZN + 0/0Y
Power Loss from Wire
Power loss = Current ^2 x resistance
P=I^2R
Transmitting Electricity
IpVp=IsVs
Primary current x Primary voltage = Secondary Current x Secondary Voltage
IpVp= power input at primary coil
IsVs=power output at secondary coil
Transformer Equation
Vp/Vs = Np/Ns
Input(primary)voltage/output(secondary)voltage = number of turns on primary coil/number of turns on secondary coil
Equation that links two resistances with the potential difference across them
R1/R2 = V1/V2
Potential difference in parallel circuits
Vsource = V1 = V2
Current in parallel circuit
Isource = I1 + I2 + …
Combined Resistance of parallel
1/Rtotal = 1/R1 + 1/R2
Potential difference in series
Vsource= V1 + V2 + …
EMF
EMF sources add up eg 1.5V + 1.5= 3V
Resistance in Series
Rtotal= 2+3 = 5 Ohms
Current in Series
I1 = I2
Current same everywhere
Energy transferred in electricity
Electricity transferred (kWh) = Power(kW) x Time(h)
Cost of energy
Cost (p) = E x Price
Cost(p) = Energy Transferred(kWh) x Price per kWh(p per kWh)
Electrical Power
Electrical Power (W) = Current(A) x Potential Difference(V)
P=IV
Energy Transferred
Energy transferred = Current x Potential Difference x Time
E=IVt
Resistance
Resistance (Ohms) = Potential Difference(V)/Current(A)
R = V/I
Current,Charge,Time
Current(A)=Charge(C)/Time(s)
I=Q/T
Work Done,PD,Charge
Potential Difference(V) = Work Done(J)/Charge(C)
V=W/Q
EMF,work done,charge
EMF(V)=Work done(J)/ Charge(C)
E=W/Q
1 Hz =?
1 wave per second
Refractive Index and law of reflection
n = sini/sinr
Critical Angle
n = 1/sinc
Law of Reflection
Sini=Sinr
Critical Angle,light in material,light in vacuum
Refractive Index = Speed in vacuum / Speed in material
Ultrasound
> 20kHz
Wave speed,wavelength ,frequency
Wave speed (m/s) = frequency(Hz) x wavelength (m)
V = F x h
Specific Heat Capacity
Change in energy = specific heat capacity(J/kg°C) x mass(kg) x temperature change
E=MC x Change in T
Specific Latent Heat
E=ML
Energy Transfer = Mass x Latent Heat(J/kg)
Constant Temp,Decreasing volume,increase pressure
PV = Constant
Pressure,Temperature
P1/T1 = P2/T2
Pressure1/Temp 1 =Pressure2/Temp2
Boyle’s Law
Pressure1 x Volume1 = Pressure2 x Volume 2
P1V1=P2V2
Liquid Density
Change in Pressure (Pa) = density of liquid(kg/m^3) x gravity(N/kg) x Change in depth(m)
Change P = d x g x change h
Pressure
Pressure(Pa)= Force(N)/ Area(m^2)
P= F/A
Efficiency
Efficiency = Useful energy output / total energy input x 100
Efficiency pt2
Efficiency = Useful power output/total power input x 100
Work Done,energy transfer,time
Power = Work Done / Time
P=W/T
Power,energy transferred,time
Power = Energy Transferred/Time
P=E/T
1 Watt
Equals 1J
Mechanical Work Done
Mechanical Work Done = Force x Distance moved = Energy transferred mechanically
W=Fd=Change in energy
W=Fd
Work Done
Equal to energy transferred
Kinetic Energy Store
Kinetic Energy = 1/2 Mass(kg) x speed^2(m/s^2)
Ek=1/2mv^2
Change in Gravitational potential energy
Change in Gravitational Energy = Mass(kg) x Gravity(N/Kg) x change in height
E=mgh
Falling objects
Energy lost from gpe store = energy gained in the kinetic energy store
Impulse
Impulse (Ns) = Force(N) x time (s) = Change in momentum (kg m/s)
Ft = change in (mv)
Change in momentum
Force = Change in mass x velocity / change in time
F=mv/t
Change in momentum
F=P/T
Force = Change in Momentum / Change in time
Ft=change in (mv)
Momentum
P=MV
Momentum = Mass x Velocity
Moments
Moment(Nm) = force(N) x perpendicular distance (m) from the pivot
M=Fd
Hooke’s Law
Spring constant(N/cm) = Force/Load(N) / extension(cm)
K = F/X
Equilibrium
Anti-clockwise moment = clockwise moment for equilibrium
Acceleration
F = ma
Force = Mass x Acceleration (m/s^2)
Density
Density = Mass / volume
D = M/ V
1g/cm^3 = 1000kg/m^3
Mass,Weight,Gravitational Field Strength
Gravitational Field Strength(N/kg) = weight(N) / mass(kg)
W=mg
g=W/m
Acceleration
Acceleration = change in velocity/change in time
Acceleration is the change in velocity over time
Speed
Average speed = total distance / total time taken