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NEET PHYSICSKinetic TheoryMedium

Question

At what temperature will the rms speed of oxygen molecules become just sufficient for escaping from the earth's atmosphere? (Given: Mass of oxygen molecule m=2.76×1026 kgm = 2.76 \times 10^{-26} \text{ kg}, Boltzmann's constant kB=1.38×1023 J K1k_B = 1.38 \times 10^{-23} \text{ J K}^{-1})

A

2.508×104 K2.508 \times 10^4 \text{ K}

B

8.360×104 K8.360 \times 10^4 \text{ K}

C

5.016×104 K5.016 \times 10^4 \text{ K}

D

1.254×104 K1.254 \times 10^4 \text{ K}

Step-by-Step Solution

To escape Earth's atmosphere, the molecule's root mean square (rms) speed must equal the Earth's escape velocity.

  1. Formulas: RMS Speed (vrmsv_{rms}) = 3kBTm\sqrt{\frac{3 k_B T}{m}} Escape Velocity (vev_{e}) for Earth 11.2 km/s=11200 m/s\approx 11.2 \text{ km/s} = 11200 \text{ m/s}

  2. Set up the equation: 3kBTm=ve\sqrt{\frac{3 k_B T}{m}} = v_{e} Squaring both sides: 3kBTm=ve2\frac{3 k_B T}{m} = v_{e}^2 T=mve23kBT = \frac{m v_{e}^2}{3 k_B}

  3. Substitute values: m=2.76×1026 kgm = 2.76 \times 10^{-26} \text{ kg} ve=11200 m/sv_{e} = 11200 \text{ m/s}

  • kB=1.38×1023 J K1k_B = 1.38 \times 10^{-23} \text{ J K}^{-1}

T=(2.76×1026)×(11200)23×(1.38×1023)T = \frac{(2.76 \times 10^{-26}) \times (11200)^2}{3 \times (1.38 \times 10^{-23})} T=2.76×1.2544×108×10264.14×1023T = \frac{2.76 \times 1.2544 \times 10^8 \times 10^{-26}}{4.14 \times 10^{-23}} T=3.462×10184.14×1023T = \frac{3.462 \times 10^{-18}}{4.14 \times 10^{-23}} T0.8362×105 KT \approx 0.8362 \times 10^5 \text{ K} T8.362×104 KT \approx 8.362 \times 10^4 \text{ K}

This matches Option 2.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from Kinetic Theory. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSKinetic Theorytemperatureoxygenmoleculesbecomesufficient

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