what is meant by centre of mass of an object?
the centre of mass of an object is the point where the whole mass of object appears to act.

work done= F x D
GPE = mgh
KE= 1/2mv2
loss in GPE = gain in KE
power =workdone/time
power=energy/time

radiation.
good absorber/emitters
dull,black surfaces.
poor absorber/emitters
shny/white surfaces
conductions occurs vibration engery. transferring frm one molecules to another
convection: less dense rise up, creating convection crrents. colder portion,denser, sinks.

thermometer.
sensitivity: capillary tube narrower. vol of mercury in bulb.
responsiveness. glass bulb thinner

Length of unknown - length of 0/length of 100- length of 0 x 100

transverse waves.eg: waves, sea waves, electromagnetic waves
transverse waves travel in a direction perpendicular to direction of vibration

longtidual waves: eg: sound waves,
traves in a direction parrallel to direction of vibration

v=fw
v=w/t
higher pitch more wave length. higher frenquency
loudness increase. amplitude higher.

refractive index
sin i/sin r
spd of light in vacuum/ sd of light in medium

gamma rays x ray uv rays visible light infra red radiowaves.
gamma ray shortes wave length, highest frequency
radiowaves longest wave length lowest frequency
spd of 3x 10^8 in vacuum.

sound,
spd in air 330m/s
spd in water 1400m/s
spd in soild 5000m/s

I=Q/t
V=E/Q
V=IR
E=PT
P=VI

green yellow- earth wire
brown-live wire
blue-neutral wire.

live wire switch and fuse
fuse physical properties: low melthing point
melts and break the circuit when too much current pass through


VsIs=VpIp
Ns/Vs= Np/Vp
transformer: consists of primary coil and secondary coil wound around laminated soft iron core
alternating voltage applied to pri coil produces changing magnetic field linked to sec coil. prodcuing induced emf in sec coil

transmission of electrical power
electrical power are transmitted at high V low A
advantage prevent power loss as heat in cables. P=I2R

ac generator.
rectangular coil rotates btw poles of magnet, coil connected to slip rings
coil rotaes cutting magnetic field, thus emf produced in coil

radioactivity.. i think i jus die =.="

thats alll im freaking stressed up right now.