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Question: Answered & Verified by Expert
\( 2 \mathrm{~kg} \) of a monoatomic gas is at a pressure of \( 4 \times 10^{4} \mathrm{~N} \mathrm{~m}^{-2} \). The density of the gas is \( 8 \mathrm{~kg} \mathrm{~m}^{-3} \). What is the order of energy of the gas due to its thermal motion?
PhysicsKinetic Theory of GasesJEE Main
Options:
  • A \( 10^{5} \mathrm{~J} \)
  • B \( 10^{6} \mathrm{~J} \)
  • C \( 10^{4} \mathrm{~J} \)
  • D \( 10^{3} \mathrm{~J} \)
Solution:
2748 Upvotes Verified Answer
The correct answer is: \( 10^{4} \mathrm{~J} \)

Internal energy is the energy due to thermal motion.

The internal energy of an ideal gas given by
U=f2nRT (for n moles)
U=f2PV=f2×P×Mρ (Since, f=3  for a monoatomic gas.)
U=32×4×104×28
=1.5×104J
So, the order of energy due to thermal motion is 104

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