Equations Flashcards
Pressure?
Force / area
P = F/A
Distance travelled?
Speed x time
S = v t
Acceleration?
Change in velocity / time taken
a = v - u / t
Wave speed?
Frequency x wavelength
V = f a
Charge?
Current x time
Q = I t
Potential difference?
Current x resistance
V = I R
Electrical Power (1)?
Potential difference x current
P = V I
Power (2)?
(Current²) x resistance
P = I²R
General power?
Energy transferred / time
P = E/t
Energy transferred?
Charge x potential difference
E = Q V
Density?
Mass / volume
rho = m/v
Period?
1 / frequency
Boyle’s Law?
pV = constant
Newton’s 2nd Law?
Acceleration = force / mass
a = F / m
Weight?
Mass x gravitational field strength
w = m g
Work done?
Force x distance moved
W = F D
Hooke’s law?
Force = spring constant x spring extension
F = k e
Resistance?
Potential difference / Current
R = V/I
Efficiency?
Useful energy / Energy put in x100
E= useful/input x100
Kinetic energy?
1/2 x Mass x Speed²
Ek=1/2mv²
Gravitational potential energy?
Mass x Gravitational field strength x Height
Ep=mgh
Velocity²?
Initial velocity² + 2 x Acceleration x Displacement
v²=u²+2as
Elastic potential energy?
1/2 x Spring constant x Extension²
Ee=1/2ke²
Specific heat capacity?
Energy / mass x temperature change
c = E / m x temp.
Specific latent heat?
Energy / mass
l = E / m
Pay back time?
Cost of insulation / Annual saving
No. of units used?
Power x Time
Pt
Total cost of electricity?
No. of units used x Unit price
Transformer?
Np/Ns = Vp/Vs
Moments?
M = F x d
Pressure at a certain depth due to the column of liquid above?
Pressure = depth x field strength x density
p=hρg
Momentum?
Mass x Velocity
m = m x v
Force (in terms of momentum)?
Change in momentum / time taken
F = ΔP / Δt
