Formulas Flashcards
Pressure
Pressure (Pa) = Force (N) / Area (m²)
Density
Density = Mass / Volume
Speed
Speed (m/s) = Distance (m) / time (s)
Velocity
Velocity (m/s) = Displacement (m) / time (s)
Acceleration
Acceleration (m/s²) = Velocity (m/s) / time (s)
Force
Force (N) = Mass (kg) * Acceleration (m/s²)
Force (N) = Mass (kg) * 9.8 m/s²
Gravitational field strength
Gravitational field strength (N/kg) = Weight (N) / Mass (kg)
Gravitational potential energy
Gravitational potential energy (J) = Mass (kg) * Gravity (9.8) * Height (m)
Kinetic energy
Kinetic energy (J) = ½ * Mass (kg) * [velocity (m/s) ]²
Pressure in liquids
Pressure in liquids (Pa) = Depth (m) * Density (kg/m³) * 9.8 N/kg (gravitational field strength)
Momentum
Momentum (kgm/s) = Mass (kg) * Velocity (m/s)
Impulse
Impulse (Ns) = Force (N) * Time (s)
Impulse (kgm/s) = Final momentum - Initial momentum
Work
Work (J) = Force (N) * Distance (m)
Work (J) = Change in Energy (J)
Power
Power (W) = Work (J) / Time (s)
Power (W) = Energy transferred (J) / Time (s)
Moment/turning force
Moment/turning force (Nm) = Force (N) * Distance perpendicular from pivot (m)
Energy efficiency
Energy efficiency (J) = (Useful energy output (J) / Energy input (J) ) * 100
Spring Constant
Spring Constant (N/m) = Force (N) / Extension (m)
Wave speed
Wave speed (m/s) = frequency (Hz) * Wavelength (m)
Reflective angle law
Angle of incidence = Angle of reflection
Refractive index
Refractive index = Speed of light in vacuum / speed of light in a substance
Refractive index = Sin (Angle of incidence) / Sin (Angle of reflection)
Refractive index = 1 / Sin (Critical angle)
Critical angle
Critical angle = Sin-1 (1/ Refractive index)
Current
Current (Amps) = Charge (Coulombs) / Time (seconds)
I = Q/t
Current (Amps) = Potential difference (Volts) / Resistance (ohms)
I = V/R V = IR
EMF
EMF (Volts) = Work done (J) / Charge (C)
Power (electricity)
Power (W or J/s) = Current (Amps) * Potential difference (Volts)
Power (W or J/s) = Energy (J) / time (s)
P = IV P = E/t E/t = IV → E = IVt P = IV, V = IR → P = I²R I = V/R, P = IV → P = V²/R
Energy (electricity)
Energy (J) = Power (Watt) * Time (s)
(bc P = E/t)
Energy (kWh) = P (kW) * Time (h)
Series –> Voltage, current, resistance
(Series), Vtotal = V1 + V2 + V3
(Series) Itotal = I1 = I2 = I3
(Series) Rtotal = R1 + R2 + R3
Parallel –> Voltage, current, resistance
(Parallel) Vtotal = V1 = V2 = V3
(Parallel) Itotal = I1 + I2 + I3
(Parallel) 1/Rtotal = 1/R1 + 1/R2 + 1/R3
. vs x
. = Coming out of the page
x = Going into the page
Transformer formulas
Vp/Vs = Np/Ns
VpIp = VsIs
(Because power stays the same → Cannot be created or destroyed)
Efficiency of transformers
Efficiency of transformers = Pout/ Pin = (IsVs / IpVp) * 100
Beta particles
Beta particles = AZX → A+0Z+1Y + 0-1e
Alpha particles
Alpha particles = XAZ → YA-4Z-2 + a42
Gamma particles
Gamma particles = XAZ → YAZ + 00 Y
Number of remaining nuclei (counts/s)
Number of remaining nuclei (counts/s) = Original amount (counts/s) / 2n
(n = number of halflife’s occurred)
Specific heat capacity - Formula
Specific heat capacity = (Change in energy) / (Mass * Change in temperature)
Energy (Joules
Mass (Kg)
Temperature (degrees Celsius or Kelvin)
Units of specific heat capacity = J/(kgK) or J/(KgC)
Hubble constant
Hubble constant (H0) is the ratio of an objects speed in which it is moving away from earth, to its distance from earth.
H0 = v/d
v - receding speed (m/s)
d - distance from earth (m)
The numerical value of the hubble constant is 2.2 * 10⁻¹⁸ per second.
(applies to all galaxies measured + can therefore be used to estimate the age of the universe)
How it the age of the universe estimated?
H0 = v/d
v = d/t –> t = d/v
–> 1/H0 = d/v = t
t = 1/ (2.2*10⁻¹⁸) = 4.5 *10¹⁷ seconds = 14 billion years
