Lect03_[Compatibility_Mode]

# Lect03_[Compatibility_Mode] - Physics 344 Foundations of...

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Physics 344 Foundations of 21 st Century Physics: Relativity, Quantum Mechanics and heir Applications Their Applications Instructor: Dr. Mark Haugan Office: PHYS 282 [email protected] TA: Dan Hartzler Office: PHYS 7 [email protected] Grader: Shuo Liu Office: PHYS 283 [email protected] Office Hours: If you have questions, just email us to make an ppointment e enjoy talking about physics! appointment. We enjoy talking about physics! Notices: Read chapter 2 of the text and start homework this weekend. irst help session Tuesday in PHYS 160 from 1:30 to 3:30 First help session Tuesday in PHYS 160 from 1:30 to 3:30.

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Last lecture and during recitation yesterday we analyzed a simple experimental situation in which a particle’s velocity had to be measured. This allowed us to reexamine the concept of an inertial coordinate system and to make the point that in relativistic situations we must be careful to distinguish between hen some physical event happens at a particular location and when an when some physical event happens at a particular location and when an observer at some other location perceives (sees, hears, …) that the event has happened. - v G To recap: We considered an electron moving freely past three detectors Detector 1 Detector 2 and Clock Detector 3 and we found that to measure its velocity we had distinguish between the times t1, t2 and t3 at which it passed the detectors and the times T1, T2 and T3 at which an observer at D2 received light signals from each detector dicating that those events had happened. indicating that those events had happened.
- v G Detector 1 Detector 2 and Clock Detector 3 More specifically, we found that py , 11 2 2 3 3 / / T t xc =+ Δ = Δ because the detector pairs were a distance Δ x apart so that it took a time terval /c r e signals from the events at t1 and t3 to reach D2 This implies that 21 2 1 2 1 21 (/ ) / / TT T tt x c t x c T T t xc t t Δ ≡−= −+ Δ = Δ Δ Δ =Δ +Δ interval Δ x/c for the signals from the events at t1 and t3 to reach D2. 32 3 2 3 2 32 // T Δ≡ = + = Δ + Δ So, if we mistakenly use the Δ Ts instead of the Δ ts to calculate the particle’s velocity obtain incorrect results x x v Δ Δ 21 21 21 /( 1 / ) 1 / xx Tt x c t v c v c x v ΔΔ == = Δ Δ Δ = during the first interval during the second one 32 32 21 1 / ) 1 / T tx c tv c v c + ++ Measuring distances and time intervals between the correct pairs of events is clearly crucial as we analyze relativistic situations in which v c .

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Inertial Coordinate Systems The process of setting up the coordinate system we used to represent the preceding experimental situation allowed us recall that inertial coordinate
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Lect03_[Compatibility_Mode] - Physics 344 Foundations of...

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