Back to Topic 1.5 — Galilean and special relativity (HL)
1.5.3Physics HL12 flashcards

Lorentz transformations

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Card 1 of 121.5.3
1.5.3
Question

State the Lorentz factor formula.

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All 12 Flashcards — Lorentz transformations

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Card 1formula

Question

State the Lorentz factor formula.

Answer

$\gamma = \dfrac{1}{\sqrt{1 - v^2/c^2}}$ — and it is **always ≥ 1**.

Card 2definition

Question

What is 'proper time' Δt₀?

Answer

The time between two events measured by a **single clock present at both** — the **shortest** possible time.

Card 3definition

Question

What is 'proper length' L₀?

Answer

The length of an object measured **in its own rest frame** — the **longest** possible length.

Card 4formula

Question

State the time-dilation formula.

Answer

$\Delta t = \gamma\,\Delta t_0$. Since γ ≥ 1, **moving clocks run slow**.

Card 5formula

Question

State the length-contraction formula.

Answer

$L = \dfrac{L_0}{\gamma}$. Since γ ≥ 1, **moving objects contract** along the motion.

Card 6process

Question

Time: multiply or divide by γ?

Answer

**Multiply** the proper time by γ ($\Delta t = \gamma\,\Delta t_0$) — the time gets bigger.

Card 7process

Question

Length: multiply or divide by γ?

Answer

**Divide** the proper length by γ ($L = L_0/\gamma$) — the length gets smaller.

Card 8example

Question

γ for v = 0.80c?

Answer

$\gamma = \dfrac{1}{\sqrt{1 - 0.80^2}} = \dfrac{1}{\sqrt{0.36}} = 1.67$.

Card 9concept

Question

Which dimension contracts in length contraction?

Answer

Only the dimension **along the direction of motion**; width and height are unchanged.

Card 10formula

Question

State the relativistic velocity-addition formula.

Answer

$u' = \dfrac{u - v}{1 - uv/c^2}$ — it always keeps the result **below c**.

Card 11example

Question

Add 0.50c and 0.50c relativistically — what do you get?

Answer

$\dfrac{1.00c}{1 + 0.25} = 0.80c$, **not** 1.0c.

Card 12comparison

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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