  We have obtained K-band Multi-Object Spectrograph (KMOS) near-IR spectroscopy
for 14 red supergiant stars (RSGs) in the young massive star cluster NGC 2100
in the Large Magellanic Cloud (LMC). Stellar parameters including metallicity
are estimated using the J-band analysis technique, which has been rigorously
tested in the Local Universe. We find an average metallicity for NGC 2100 of
[Z]=$-$0.43$\pm$0.10 dex, in good agreement with estimates from the literature
for the LMC. Comparing our results in NGC 2100 with those for a Galactic
cluster (at Solar-like metallicity) with a similar mass and age we find no
significant difference in the location of RSGs in the Hertzsprung--Russell
diagram. We combine the observed KMOS spectra to form a simulated
integrated-light cluster spectrum and show that, by analysing this spectrum as
a single RSG, the results are consistent with the average properties of the
cluster. Radial velocities are estimated for the targets and the dynamical
properties are estimated for the first time within this cluster. The data are
consistent with a flat velocity dispersion profile, and with an upper limit of
3.9 km/s, at the 95% confidence level, for the velocity dispersion of the
cluster. However, the intrinsic velocity dispersion is unresolved and could,
therefore, be significantly smaller than the upper limit reported here. An
upper limit on the dynamical mass of the cluster is derived as $M_{dyn}$ $\le$
$15.2\times10^{4}M_{\odot}$ assuming virial equilibrium.
