Answer
$V=55.14\ m/s=198.5\ km/h$
Work Step by Step
The energy balance for the hand:
$Q_{hand}=\Delta KE=\frac{m_{hand}}{2}(0-V^2)$
The energy balance for the tissue:
$Q_{tissue}=\Delta U= m_{tissue}c\Delta T$
With $Q_{tissue}=-Q_{hand}$
$V^2=\frac{2}{m_{hand}}m_{tissue}c\Delta T$
With $m_{hand}=0.9\ kg,\ m_{tissue}=0.15\ kg,\ c=3.8\ kJ/kg.K,\ \Delta T=2.4\ K$
Hence $V=55.14\ m/s=198.5\ km/h$
