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Explore Einstein's Laws of Motion and Galilean Relativity, including the concepts of inertial and non-inertial frames. Learn about the Michelson-Morley experiment and Einstein's principles of special and general relativity.
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First Law • Newton’s first law says that with no net force there is no acceleration. • Objects at rest • Objects at constant velocity • If there is no observed acceleration on an object with no net force, the observer is in an inertial reference frame. • Newton’s laws of mechanics apply equally • No absolute motion
Inertial Frame • An observer on the table sees two ball fall. • First straight down • Second in a curve • An moving with the second ball sees the reverse. • Second straight down • First in a backwards parabola • Both frames are inertial. • Motion consistent with Newton
A rotating observer throws a ball across a merry-go-round. Ball veers to the side No external force This is a non-inertial frame. Observed motion inconsistent with Newton’s laws Fictitious forces Accelerated Frame
Galileo described the conversion between inertial frames in 1638. Galilean relativity Basis for Newton The Galilean transformation describes velocities as sums. Galilean Relativity v y S y’ S’ x EventP x’ x x’
Light as a wave should have a medium for transmission. Velocity like a plane in the wind Speed c without motion The earth’s velocity and the light velocity must add to get the result from the earth. Moving Light medium observed source light
Michelson-Morley • An interferometer can split and recombine light. • Interference shifts for different paths • In 1887 an experiment sowed the direction didn’t matter. • The speed c must be a universal constant. mirror 2 semi-silvered mirror mirror 1
In 1905 Einstein described two basic principles. The laws of physics are the same in all inertial frames. The speed of light in a vacuum is the same for all inertial frames, from all sources. Einstein’s Principles
Equivalence Principle • The 1905 principles became known as special relativity. • In 1915 Einstein added another principle to form general relativity. • Gravitational mass is the same as inertial mass. descsite.nl