The joint which is made between two rails toger with two fish plates and four fish bolts to form an expansion gap of 1.5 to 3 mm. Rail joint is weakest part in railway track.

Liquid flows under atmospheric pressure in an open channel due to its slope of channel. There must be some slope in bed of channel to flow to take place.

Sleepers are transverse ties on which rails are laid and transfer load from rails to ballast. The main function of a sleeper is to provide a firm and even support to rails.

When liquid flows at a velocity that is less than critical velocity. A thin stationary film of liquid is formed on a supporting surface. This is a reason that frictional resistance is independent of nature of surface of contact.

A perfect frame is 1 for which following equation is satisfied m = 2j-3.
A perfect frame is that which is composed of members just sufficient to keep it in equilibrium when loaded without any change.

The ratio of inertia force and gravity force is known as Froude number. It is denoted by Fr.
Fr = V/(gD)1/2.

Reynold?s number (Re) = Vd/v
V = Mean velocity of flow in pipe
d = Diameter of pipe
v = Kinematic viscosity of liquid
Flow in circular pipe will be turbulent if Reynolds number is greater than 2800.

For each rail joint, four fish bolts are required to connect fish plates and rails toger. Fish bolts are made of medium or high carbon steel to which stand heavy stresses.

Seal code is final coat lay over bituminous pavements which are not impervious. Seal coat develops skid resistant texture and y provide better riding surface.

An artificial channel is one which is built artificially for some specific purpose such as irrigation water supply and water power development etc. The examples include canals, drainage gutters and aqueducts.