Formulae Flashcards
state the equation linking average speed, distance and time
average speed(m/s) = distance(m) ÷ time(s)
state the equation linking force, mass and accelaration
force (N) = mass (kg) x acceleration (m/s²)
state the equation linking acceleration, velocity and time
acceleration(m/s²) = change in velocity(m/s) ÷ time taken(s)
state the equation linking density, mass and volume
density (g/cm³) = mass(g) ÷ volume(cm³)
state the equation linking force, distance and work done
work done(J) = force(N) x distance moved in direction of force(m)
state the equation linking mass, weight and gravitational field strength
weight(N) = mass(kg) x gravitational field strength(N/kg))
state the equation linking pressure, force and area
pressure(N/cm²) = force(N) ÷ area(cm²)
state the equation linking moment of a force and distance from pivot
moment(Nm) = force(N) x perpendicular distance from pivot(m)
state the equation linking charge, current and time
charge(C) = current(A) x time(s)
or
Q=IT
state the equation linking voltage, current and resistance
voltage(V) = current(A) x resistance(Ω)
or
V=IR
state the equation linking power, current and voltage
power(W) = current(A) x voltage(V)
or
P=IV
state the equation linking wave speed, frequency and wavelength
wave speed(m/s) = frequency(Hz) x wavelength(m)
state the equation for the refractive index
n = sin(i) ÷ sin(r)
state the equation for the critical angle
sin(c) = 1 ÷ n
state the equation for pressure difference
pressure difference(Pa) = height(m) x density(kg/m³) x g(N/kg)
state the equation for efficiency
efficiency = useful energy output ÷ total energy input
state the equation for gravitational potential energy
GPE(J) = mass(kg) x height(m) x gravitational field strength(N/kg)
state the equation for kinetic energy
KE(J) = 1/2 x mass(kg) x speed²(m/s)
state the equation for energy transferred and work done
energy transferred = work done
state the equation linking momentum, mass and velocity
momentum(kgm/s) = mass(kg) x velocity(m/s)
state the equation linking voltage, energy and charge
voltage(V) = energy(J) ÷ charge(C)
state the transformer relationship between voltage and turns
input (primary) voltage ÷ output (secondary) voltage = primary turns ÷ secondary turns
state the transformer relationship for 100% efficiency
input power = output power
V1 x I1 = V2 x I2
state the equation linking energy transferred, current, voltage and time
energy transferred(J) = current(A) x voltage(V) x time(s) or energy transferred (J) = power (W) x time(s)
state the equation for frequency
frequency(Hz) = 1 ÷ time period(s)
state the principle of conservation of momentum
momentum after = momentum before
state the equation linking work done, power and time taken
power(W) = work done(J) ÷ time taken (s)
State the equation linking time taken, change in momentum and force
Force = change in momentum ÷ time taken
state the equation linking pressure, volume and temperature for a gas
P1 x V1 = P2 x V2
T1 T2
NB: temperature MUST be in KELVINS