Formulas and units Flashcards
speed equation
v= s/t (speed= displacement/time)
average speed equation
average speed= total distance travelled/total time taken
acceleration equation
a= ∆v/∆t (acceleration= final velocity - initial velocity/ change in time)
weight equation
W=mg (weight= mass x gravitational field strength)
force equation
F=ma (Force= mass x acceleration)
density equation
ρ = m/V (density= mass/volume)
pressure formula
P=F/A (pressure= force/area)
fluid pressure formula
P=ρgh (pressure= density x gravitational field strength x height/depth)
spring constant equation
k = F/x (spring constant= force/extension)
moment formula
moment = force × perpendicular distance from the pivot
momentum formula
p= mv (momentum = mass x velocity)
impulse formula
impulse = force x time for which force acts
impulse = F∆t = ∆(mv)
force formula
F = ∆p/∆t
work equation
W= Fd (work= force x parallel distance
kinetic energy equation
Ek= 1/2mv^2 (kinetic energy= 1/2 x mass x velocity^2)
gravitational potential energy equation
∆Ep = mg∆h (gravitational potential energy = mass x gravitational field strength x height)
What is work equal to?
∆E (change in kinetic energy)
Power equation (mechanical)
P=W/t (power= work/time)
also P=∆E/t
Power equation (electric)
P=VI (power= voltage x current)
percentage efficiency equation
(%) efficiency = (useful energy output)/(total energy input) (× 100%)
(%) efficiency = (useful power output)/ (total power input) (× 100%)
Temperature in kelvin equation
T (in K) = θ (in °C) + 273
Equation for fixed mass of gas at constant temp
pV = constant
heat capacity equation
c = ∆E/m∆θ
wave speed equation
v = fλ
energy (latent heat) equation
e=mL (energy = mass x specific latent heat)
pressure and volume temperature equation
pV=nRT (pressure x volume = moles x gas constant x temperature in kelvin)
refractive index equations
n = sin(i)/sin(r)
n = 1/sin(c)
Refractive index (n) = speed of light in vacuum or air (c)/speed of light in medium (V)
frequency equation
f= 1/T
(frequency = 1/period)
charge equation
Q=It (charge = current x time)
potential difference and electromotive force equation
E or V= W/Q (emf or pd = work done/ charge quantity)
electric energy equation
E=VIt (power x time)
resistance equation
R=V/I (voltage/resistance)
equation for potential divider
R1/R2=V1/V2 (resistance 1/resistance 2 = voltage 1/voltage 2)
power in wires equation
P=I^2R (power= current^2 x resistance)
Equation for 100% efficiency transformer
I(p)V(p)=I(s)V(s)
current (primary) x potential difference (primary) = current (secondary) x potential difference (secondary)
Transformer equation
V(p)/V(s) = N(p)/N(s)
(potential difference primary/ potential difference secondary = number of turns primary/ number of turns secondary)
orbital speed equation
v = 2πr/T (speed= 2 x pi x average radius of orbit/ orbital period)
Hubble constant equation
H0=v/d (Hubble constant= speed at which galaxy is moving away from the earth/ distance from the earth)
age of universe equation
1/H0= d/v
Current estimate for hubble constant
2.2 × 10^–18 per second
