Lorentz transformations
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All 12 Flashcards — Lorentz transformations
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Question
State the Lorentz factor formula.
Answer
$\gamma = \dfrac{1}{\sqrt{1 - v^2/c^2}}$ — and it is **always ≥ 1**.
Question
What is 'proper time' Δt₀?
Answer
The time between two events measured by a **single clock present at both** — the **shortest** possible time.
Question
What is 'proper length' L₀?
Answer
The length of an object measured **in its own rest frame** — the **longest** possible length.
Question
State the time-dilation formula.
Answer
$\Delta t = \gamma\,\Delta t_0$. Since γ ≥ 1, **moving clocks run slow**.
Question
State the length-contraction formula.
Answer
$L = \dfrac{L_0}{\gamma}$. Since γ ≥ 1, **moving objects contract** along the motion.
Question
Time: multiply or divide by γ?
Answer
**Multiply** the proper time by γ ($\Delta t = \gamma\,\Delta t_0$) — the time gets bigger.
Question
Length: multiply or divide by γ?
Answer
**Divide** the proper length by γ ($L = L_0/\gamma$) — the length gets smaller.
Question
γ for v = 0.80c?
Answer
$\gamma = \dfrac{1}{\sqrt{1 - 0.80^2}} = \dfrac{1}{\sqrt{0.36}} = 1.67$.
Question
Which dimension contracts in length contraction?
Answer
Only the dimension **along the direction of motion**; width and height are unchanged.
Question
State the relativistic velocity-addition formula.
Answer
$u' = \dfrac{u - v}{1 - uv/c^2}$ — it always keeps the result **below c**.
Question
Add 0.50c and 0.50c relativistically — what do you get?
Answer
$\dfrac{1.00c}{1 + 0.25} = 0.80c$, **not** 1.0c.
Question
Time dilation vs length contraction — key difference?
Answer
Time **stretches** (Δt = γΔt₀, multiply); length **shrinks** (L = L₀/γ, divide). Both use the same γ.
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Topic 1.5 hub
Galilean and special relativity (HL)
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