Solution:

Ruling gradient ? The ruling gradient is the steepest gradient that exists in a section. It determines the maximum load that can be hauled by a locomotive on that section. ? While deciding the ruling gradient of a section, it is not only the severity of the gradient but also its length as well as its position with respect to the gradients on both sides that have to be taken into consideration.

Pusher or helper gradient ? In hilly areas, the rate of rise of the terrain becomes very important when trying to reduce the length of the railway line and, therefore, sometimes gradients steeper than the ruling gradient are provided to reduce the overall cost. ? In such situations, one locomotive is not adequate to pull the entire load, and an extra locomotive is required

Momentum Gradient ? The momentum gradient is steeper than the ruling gradient and can be overcome by a train because of the momentum it gathers while running on the section. ? In valleys, a falling gradient is sometimes followed by a rising gradient. In such a situation, a train coming down a falling gradient acquires good speed and momentum, which gives additional kinetic energy to the train and allows it to negotiate gradients steeper than the ruling gradient. ? In sections with momentum gradients there are no obstacles provided in the form of signals, etc., which may bring the train to a critical juncture.