Final answer:
There is a force of friction known as rolling friction between the wheels of a moving train and iron rails, which is minimized to make trains an energy-efficient transportation system.
Step-by-step explanation:
Yes, there is a force of friction between the wheels of a moving train and iron rails. This type of friction is known as rolling friction. Rolling friction occurs when a wheel rolls over a surface and, due to its nature, it is much smaller compared to other types of friction, such as static friction or kinetic friction. In the context of trains, this reduced friction is what makes them very energy-efficient forms of transportation.
When the train is moving, the contact points on the wheels are continuously changing, which helps minimize friction. Moreover, the wheels and tracks are designed to have a very smooth interaction to decrease rolling friction further. As a result, trains can transport heavy loads over long distances with relatively less energy compared to vehicles relying on kinetic friction.