Why do freight trains have multiple engines at the front and rear?

Question

I always wondered what the extra locomotives are for on modern freight trains, are they for extra power?

In: Engineering

Answer 1

When multiple engines are connected, in physics it’s known as a connected body. In connected bodies, to calculate the force, you add the masses of all the objects then multiply by the acceleration. So the more mass that is accelerating directly effects the force that the train can pull

([Train1 mass] + [Train2 mass]) * acceleration

If you have 2 identical engines connected, it’s the equivalent to one at double the acceleration