## College Physics (4th Edition)

The change in the internal energy of the engine is $~94.5~J$
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 $~94.5~J$