physics

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