Question

The electric motor of a model train accelerates the train from rest to 0.620 m/s in 21.0cs. The total mass of the train is 875 g. Find the average power delivered to the train during the acceleration.

Answer 1

The average power delivered to the train during the acceleration can be found as follows:

$$P=\dfrac{W}{t}.$$

We can find the work done by the electric motor from the work - kinetic energy theorem:

$$W=KE_f-KE_i=\dfrac{1}{2}mv_f^2.$$

Finally, we get:

$$P=\dfrac{0.875\ kg\times(0.620\ \dfrac{m}{s})^2}{2\times21.0\times10^{-3}\ s}=8.01\ W.$$