formulas and units Flashcards
state hookes law
force= constant * extension
F=Kx
formula for moment
force * distance from pivot (at 90degrees)
F1d1 = F2d2
F1d1 + F2d2 = F3d3
pythagoras
aˆ2 = bˆ2+ cˆ2
force
mass x acceleration
mass=kg, a =m/s2
weight
mass * gravity
gravity= 9.8m/sˆ2
momentum
mass x velocity
impulse
= Force x contact time = change in momentum
velocity/speed
distance/time
acceleration
change in velocity / change in time
density
mass/volume
pressure laws in gas
1/volume
p1v1=p2v2
work
Force x distance (parallel to Force)
potential energy
mass x gravity x height
kinetic energy
= ½ x mass x (velocity)2
power. 4
work done/time taken
current * voltage
current ˆ2 * resistence
voltage ^2/ resistence
pressure
force/ area
pressure in liquids
= density x gravity x depth
current
charge/ time
potential difference (voltage)
work done/ charge
e.m.f
work done/ charge
ohms law
voltage= current * resistence
resistance
voltage/current
energy
voltage * current * time
resistence laws
bigger the length of wire, bigger the resistence
bigger the diameter of wire smaller the resistence
resistence in series
r= r1 +r2
resistence in parallel
r= r1 *r2/ r1+r2
potential divider
v out= (r1/ r1 + r2) * v in
r1/r2= v1/v2
heat energy
mass x specific heat capacity x temperature change
efficiency
(useful Energy (or power) output/ Energy (or power) input) * 100%
wave speed
frequency x wavelength
frequency
number of oscillations/ time taken
1/T
refractive index
sin 1/ sin r
v1/v2
1/sin c
speed of light in a vacum
3 * 10ˆ8 m/s
speed of sound in air
330 to 350 m/s
human audible range
20-20000 hz
transformers
number of turns in primary coil/ number of turns in secondary coil = voltage in primary coil/ voltage in secondary coil
voltage1 * current 1= voltage 2 * current2
orbital speed
2 π r/ period time
hubbles constant
speed/ distance
age of universe
distance/ speed
1/hubbles constant
hubbles constant number
2.2 x 10ˆ-18 per second
one light year is…
9.5 x 1015 m
milky way galaxy diameter
100 000 light years
mega
- 1000 000
kilo
- 1000
mili
/1000
unit for force and weight
newtons (N)
mass unit
g or kg
temperature unit
degrees or kelvin (k)
frequency unit
hertz (hz)
velocity speed unit
m/s or km/h
acceleration unit
m/s ˆ2
current
amps (A)
p.d votlage unit
volts (V)
charge unit
columbs (c)
resistence unit
ohms (Ω)
moments unit
Nm
momentum unit
kg m/s
power unit
watts (w)
density unit
g/cm3
, kg/m3
pressure units
Pascals (Pa), N/cm2
work and energy unit
joules (J)
electrical energy unit
kWh
specific heat capacity
J/kg0C, J/g0C
