  We present a measurement of the potential energy of an ultracold trapped gas
of $^{40}$K atoms in the BCS-BEC crossover and investigate the temperature
dependence of this energy at a wide Feshbach resonance, where the gas is in the
unitarity limit. In particular, we study the ratio of the potential energy in
the region of the unitarity limit to that of a non-interacting gas, and in the
T=0 limit we extract the universal many-body parameter $\beta$. We find $\beta
= -0.54^{+0.05}_{-0.12}$; this value is consistent with previous measurements
using $^{6}$Li atoms and also with recent theory and Monte Carlo calculations.
This result demonstrates the universality of ultracold Fermi gases in the
strongly interacting regime.
