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MP DTE Kinetic Theory — practice questions — page 2

Explore 58 free Kinetic Theory questions in MP DTE Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Kinetic Theory questions and exercises with answers

Showing questions 31–58 of 58.

If the mean free path of N₂ at 1 atm is ~80 nm, what is it at 0.01 atm (same T)?Read the answer and worked solution →The number of moles of oxygen ($O_2$) gas in a vessel of volume 1 L at STP (273.15 K, 1.013 × 10⁵ Pa) is approximately:Read the answer and worked solution →For a body on a horizontal surface, the NORMAL FORCE N equals:Read the answer and worked solution →A 5 kg block is pushed with 30 N along a frictionless surface. Acceleration:Read the answer and worked solution →Two equal masses (3 kg each) connected by a light string over a frictionless pulley. One on smooth horizontal table, other hangs over edge. Acceleration?Read the answer and worked solution →The ideal gas equationRead the answer and worked solution →Constants of the gas lawsRead the answer and worked solution →When real gases obey the equationRead the answer and worked solution →Pressure from molecular motionRead the answer and worked solution →Reading the pressure relationRead the answer and worked solution →What temperature measuresRead the answer and worked solution →Which moves fasterRead the answer and worked solution →Odd one out: kinetic theoryRead the answer and worked solution →Law of equipartitionRead the answer and worked solution →Equipartition, checkedRead the answer and worked solution →Mode to energyRead the answer and worked solution →Specific heats from equipartitionRead the answer and worked solution →Mean free pathRead the answer and worked solution →Free path and collisionsRead the answer and worked solution →Who proposed whatRead the answer and worked solution →Odd one out: the gas lawsRead the answer and worked solution →True of gasesRead the answer and worked solution →Forces between moleculesRead the answer and worked solution →Symbol to meaningRead the answer and worked solution →Translational kinetic energyRead the answer and worked solution →Odd one out: what changesRead the answer and worked solution →Modes and degrees of freedomRead the answer and worked solution →Kinetic theory, mixed checkRead the answer and worked solution →

Worked practice questions

If the mean free path of N₂ at 1 atm is ~80 nm, what is it at 0.01 atm (same T)?

  1. ~ 8 nm
  2. ~ 80 nm
  3. ~ 800 nm
  4. ~ 8 μm (mean free path ∝ 1/P)
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Correct answer: D. ~ 8 μm (mean free path ∝ 1/P)

λ ∝ T/P. Reducing P by 100× increases λ by 100×: 80 nm × 100 = 8000 nm = 8 μm. (Why vacuum coating works at low pressure — gas molecules don't collide before reaching the substrate.)

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The number of moles of oxygen ($O_2$) gas in a vessel of volume 1 L at STP (273.15 K, 1.013 × 10⁵ Pa) is approximately:

  1. ~ 0.045 mol
  2. ~ 0.045 g
  3. ~ 1.0 mol
  4. ~ 22.4 mol
Show answer and solution

Correct answer: A. ~ 0.045 mol

$n = PV/(RT) = (1.013\times10^5)(10^{-3})/(8.314\times273.15) = 101.3/2270.6 \approx 0.0446$ mol. Equivalently, 22.4 L = 1 mol at STP, so 1 L ≈ 1/22.4 = 0.0446 mol.

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For a body on a horizontal surface, the NORMAL FORCE N equals:

  1. mg/2
  2. mg (weight)
  3. 2mg
  4. Zero
Show answer and solution

Correct answer: B. mg (weight)

For a body at rest on a horizontal surface, N must balance gravity: N = mg. (If inclined, N = mg cos θ; if accelerating vertically, N changes accordingly.)

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More Physics topics

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