- #1
Dazed&Confused
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Homework Statement
An ideal monatomic gas is contained in a cubic container of size ##L^3##. When ##L## is halved by reversibly applying pressure, the root mean square ##x##-component of the velocity is doubled. Show that no heat enters of leaves the system.
Homework Equations
##dU = dQ -pdV##
##\langle {v_x}^2 \rangle = kT/m##
##pV = nRT##
##U = \frac{3}{2}nRT##
The Attempt at a Solution
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Since ##2\langle {v_x}^2 \rangle = k2T/m##, the temperature has doubled.
The change in internal energy is ##\Delta U = \frac{3}{2}R(2T -T) = \frac{3}{2}RT##.
The final pressure is ##p' = \frac{nR2T}{V'} = \frac{16nRT}{L^3}##.
I must somehow show that $$\int -pdV = \Delta U,$$
but I seem to know nothing about the path.