31.Why we are using 60Hz in ship even though half the world is using 50 Hz

The higher frequency means that generators and motors run at higher speeds with a consequent reduction in physical size of machinery for a given power rating. A reduction in size of the machinery is a very important issue when it comes to ship designing, as we all know ships are made to make money so lesser the size of any machinery greater the possibility to increase the cargo carrying capacity and hence make more money.