How many types of gradient are their in railway

DIFFERENT TYPES OF GRADIENT ARE: 

Ruling gradient: ruling gradient is the maximum gradient to which the track may be laid in particular section. It depends on the load of the train and additional power of locomotive. That is null power required to pull up the train of weight w moving on a track having slope theta 

                     F=w sin theta= w tan theta=w gradient

From the Above equation it is clear that the additional power required by the locomotive is directly proportional to the gradient. Steeper the gradient more will be the power required. In India for 1 locomotive train the following ruling gradient are adopted

In plains-1 in 150 to 1in 200

in hilly tracks:1in 100 to 1in 150

Momentum gradient: gradient which is steeper than the ruling gradient and where the advantage of momentum is utilised is known as momentum gradient. Train gets moment when it is in down gradient and this momentum can be utilised for a up gradient. A train coming down a gradient gains sufficient momentum. This momentum gives additional kinetic energy to the moving train which would help the train to rise a steeper gradient then the ruling gradient for certain length of the track. This rising gradient is called momentum gradient. In such gradients no signal are provided to stop the train.

Pusher gradient: pusher gradient is the gradient where extra engine is required to put the train. These are steeper gradient than ruling gradient and is provided at certain places of mountains to avoid heavy cutting or to reduce the length of the track. Pusher gradient of 1 In 37 on Western ghats with B.G tracks is length of track. On Darjeeling railway with N.G cause track ruling gradient of 1 INR 25 is provided.

Station yard gradient:station yard gradient is the minimum gradient provided in station yard for easy drainage of rain water.