Answer
The change in the internal energy of the engine is $~94.5~J$
Work Step by Step
We can find the increase in kinetic energy of the train:
$K = \frac{1}{2}mv^2$
$K = \frac{1}{2}(9.00~kg)(3.00~m/s)^2$
$K = 40.5~J$
Note that the work done by the engine is equal to the increase in kinetic energy of the train. We can find the change in the internal energy of the engine:
$\Delta U = Q-W$
$\Delta U = 135~J-40.5~J$
$\Delta U = 94.5~J$
The change in the internal energy of the engine is $~94.5~J$
