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Physics - Topic 5 & 6 - Forces & Waves, continuous spectrum -…
Physics - Topic 5 & 6 - Forces & Waves
mechanical quantites
scalar quantity
Contains only magnitude
vector quantity
contains both direction and magnitude
weight
force due to pull of gravity on an object
mass
quantity of matter in an object
resultant force
sum of all forces in all directions on an object
W = mg
Moments
turning effect of a force
gears
alter force and speed
equilibrium
clockwise moments = anticlockwise moments
moments = force x direction
m = fd
levers
act as force multipliers
Hooke's Law
work done = force x distance
force = spring constant x extension
extension of a spring is directly proportional to force applied
f = ke
E = 1/2 x k x e2
1 joule = 1 newton-metre
elastic potential energy = 1/2 x spring constant x extension2
pressure
pressure = force / area
p = f/a
measured in pascals
pressure is force per unit area
Momentum
total momentum before = total moment after
p = mv
vector quantity
momentum = mass x velocity
speed and acceleration
speed = velocity x time
speed - scalar quantity
velocity - vector quantity
distance - scalar quantity
displacement - vector quantity
acceleration = change in velocity / time taken
Newton's law
1st law
an object stays in motion or constant unless acted upon by an external force
2nd law
acceleration of a moving object is determined by its force acting on it and its mass
3rd law
if a force is exerted on one object from another, the other object exerts an equal force in the opposite direction
wave properties
wavelength
distance between two points on a wave
speed
wave speed = wavelength x frequency
period
time taken for one wavelength to pass
time period = 1 / frequency
amplitude
max displacement from rest
frequency
no of oscillations per second (Hertz)
frequency = 1 / time period
lenses
concave
virtual image
convex
real or virtual image
wave effects
reflection
angle of incidence = angle of reflection
Black body radiation
perfect black body
all radiation is absorbed and doesn't reflect or transmit
refraction
wave speed increases if away from the norm
wave speed decreases if moves towards the norm
constant frequency
transverse waves
oscillations perpendicular to direction of the energy source
electromagnetic waves
longtitudinal waves
oscillations parallel to the direction of the energy source
sound
seismic
s-waves
solids only
p-waves
solids / liquids
ultrasound
above frequency of human hearing
used in scanning
sound vibrations in eardrum - audible range 20Hz - 20kHz
continuous spectrum
gamma rays
high frequency
short wavelength
radiowaves
low frequency
long wavelength
ultraviolet
infared
microwaves
visible
x-rays