JEE Main 2022 · 29 Jul · Shift 2 · Physics Q49

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PhysicsSingle correct+4 / -1Question 49 of 90

The root mean square speed of smoke particles of mass $5\times10^{-17}$ kg in their Brownian motion in air at NTP is approximately. [Given k = $1.38\times10^{-23}$ J K $^{-1}$ ]

60 mm s

^{-1}

12 mm s

^{-1}

15 mm s

^{-1}

36 mm s

^{-1}

Answer and worked solution

Official answer: C

rms speed $\sqrt{\dfrac{3kT}m}=\sqrt{\dfrac{3\times1.38\times10^{-23}\times273}{5\times10^{-17}}}\approx0.015$ m/s = 15 mm/s.

(C)

Topics:Molecular speeds

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JEE Main 2022 · 29 Jul · Shift 2, Physics question 49