# physics

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1. When an ideal gas is expanded adiabatically in volume at constant pressure, the average kinetic energy of the gas molecule: A. Increase B. decreases C. Does no change
i know the answer is B but can someone explain why please? i thought it does not change since its adiabatically.

• physics -

The 1st law of thermodynamics
ΔQ=ΔU+W= ΔU+pΔV
0=ΔU+pΔV
if p=const and ΔV ↑ => ΔU ↓
The internal energy ΔU depends on temperature; and temperature decreases as the kinetic energy of particles decreases

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