Froude Number Formula


Froude Number Formula

Froude number was termed after William Froude is a dimensionless number defined as the ratio of characteristic velocity to the gravity wave velocity. 

Where, the characteristic velocity is v and

the characteristic wave velocity is c,

gravity in terms of the Froude number is articulated as,

Froude number is Fr,

velocity is v,

gravity is g,

characteristic length is l.

It is used to specify the resistance of a body which is immersed partially moving along with water.

Froude Number Solved Problems

Underneath are some of the solved problems based on Froude Number:

Problem 1: Find the Froude number if the length of the boat is 2m and velocity is 10 m/s.

Known: length l = 2m, velocity v = 10 m/s

The Froude number is articulated as,

Thus, the Froude number of the boat is 0.451.


Problem 2: Compute the velocity of the moving fish in the water if its length 0.5 m and Froude number is 0.72.


Known: l (length) = 0.5m, Fr (Froude number) = 0.72

The Froude number is given by,

Thus, the velocity of the moving fish is 1.59 m/s.


Practise This Question

A truck has a mass of 8000 kgs, a car has a mass of 1000 kgs and a bike has a mass of 100 kgs. Both the truck and car are moving on a level road at 45m/s.The bike, however, is going on the same level road at 55m/s. The kinetic energy will be more for the _______.