weight
force a body exerts due to the pull of gravity
mass
the measure of the amount of material in a body
momentum=
mass x velocity
density is
mass per unit volume
density=
mass/volume
friction is
a force that opposes motion
air resistance or drag
occurs when the object moves through air or fluid
reduce friction by
lubrication
friction acts in the
opposite direction of the motion of object
1st law
a body will remain at rest or move at a constant velocity if the resultant force acting on the body is zero
balanced forces exist when
two forces act in opposite directions but are the same size
2nd law
if a resultant force acts on a body the body will not remain at rest or move at constant velocity, it will accelerate
resultant force=
mass x acceleration
distance is
the total amount of ground covered
displacement is
shortest distance from start to finish in a certain direction
speed is
rate of change of distance
velocity is
rate of change in displacement
acceleration is
rate of change in velocity
scalar
has magnitude only
vector
magnitude and direction
acceleration=
velocity/time
unit of acceleration
m/s²
Work =
force x distance
unit of work
newton meter
centrepedal force depends on
mass of objectspeed of objectradius of circle
unit of momentum
kgm/s²
change in momentum=
force x time
momentum depends on
mass velocity
conservation of momentum
when two bodies collide, the total momentum remains constant, providing that there are no external forces acting
energy types
kineticlightsoundEPEGPEchemicalelectricalnuclearmagneticheat
GPE
the type of energy anything above the ground has
nuclear
energy stored inside nucleus due to its missing mass
unit of energy
joules
formula for kinetic energy=
½mv²
principle of energy
energy cannot be created or destroyed, only changed into different forms
power
rate at which work is done or energy is transferred
power=
work done/time
JJ Thompson
plum pudding modela sphere of positive charge with tiny negative electrons stuck in it
Rutherford
fired positively charged alpha particles at a thin gold foilmost alpha particles went straight through with no or little deflectionsome were deflected through very large angles and a few came straight back introduced nucleus
Bohr
introduced the idea of electrons orbiting a nucleus un discrete energy levels, by studying the emission spectra of gases
alpha α ⁴He₂
helium nucleuspositively chargeddeflected by magnetic field
nuclear fission
This is when heavy nuclei can be forced to split into two lighter nuclei
nuclear fussion
this is when two lighter nuclei combine to form a single heavier nucleus
if light enters or leaves a different material, of different optical density
the speed of light changes and therefore the direction of travel changes
light travels in
straight lines
light speed in vacuum
300000km/s
dispersion
spreading out of white light into its separate colours
conditions of total internal refraction
light must be travelling from a more optically dense material to a less optically dense materialangle of incidence is greater than the critical angle for the given material
waves are produced
by vibrations
waves
transfer energy from one point to another in the direction in which the wave is travelling, without the movement of material as a whole
transverse waves
direction of travel of the wave is perpendicular to the direction of vibrations e.g. mexican wave
longitudinal wave
direction of travel of the wave is parallel to the direction of vibration e.g. audible sound
amplitude A
the maximum displacement from the equilibrium position
period T
time taken for one complete vibration
wavelength λ
distance between two neighbouring crest/troughs or compression/rarefactions
frequency F
number of complete vibrations occurring in one second
period=
1/frequency
wave speed=
frequency x wavelength
when waves are reflected the
speed frequency and wavelength fo not change
when waves are refracted the
frequency does not change
electromagnetic spectrum
group of waves that all have the same speed
average velocity=
total displacement/total time
net force=
mass x acceleration
GPE=
mgh
Electric Field lines point
away from positive charges
Gravitation force is related to distance
inverse square
Relationship between current and resistance
inverse
Relationship between voltage and current
direct
Relationship between mass and centripetal acceleration
none
relationship. between speed and kinetic energy
exponential
relationship between force and change in spring length
direct
relationship between PEs and change in spring length
exponential