Physics Relativity

Newtonian physics

assumes time and space are absolute and velocities add linearly

Inertial frame of reference

object not accelerating moving at constant velocity or at rest

Non inertial frame of reference

frame that is accelerating relative to an inertial frame

Galilean transformation

used in Newtonian mechanics assumes time is the same for all observers

Lorentz transformation

used in relativity accounts for time dilation and length contraction

Einstein first postulate

laws of physics are the same in all inertial frames

Einstein second postulate

speed of light in a vacuum is constant for all observers

Speed of light

value c is 3.0 x 10^8 m s^-1 and is invariant

Simultaneity

events simultaneous in one frame may not be simultaneous in another

Time dilation

moving clocks are observed to run slower than stationary clocks

Length contraction

length decreases in the direction of motion for a moving observer, and or a moving object

Relativistic velocity addition

velocities combine using u = (v + u') / (1 + vu'/c^2)

Muon evidence

muons detected at Earth surface due to time dilation and length contraction

Michelson Morley experiment

null result shows speed of light same in all directions

Gravitational force

Fg = G m1 m2 / r^2

Universal gravitational constant

G = 6.67 x 10^-11 N m^2 kg^-2

Gravitational field

region where a mass experiences a force

Weight

F = mg

Gravitational field strength

g = F/m = GM/r^2

Inverse square law

force proportional to 1/r^2

Centripetal force

Fc = mv^2 / r

Orbital motion

Fg provides centripetal force

Kepler third law

T^2 / r^3 = constant

Stable orbit

Fg = Fc

Spiralling inward

Fg greater than Fc

Spiralling outward

Fg less than Fc

Barycentre

common centre of mass around which objects orbit