Why Air Conditioner (AC) capacity is measured in tons?

Most of us are using Air Conditioner to fight with summer heat. It makes everyone to feel relaxed in summer. Do you ever observe the specification of air conditioner. You will find that its cooling capacity is measured in ton and not in KW or something else. Why it is in tons?

Why do sand is sprayed on railway track by engine?

Almost everyone must travelled in train. It is the most common means of transport. Trains are used for moving both passengers and goods from one place to another. We all know that train is run by a rail engine. Do you know, apart from energy sources, the most important thing to run a train is sand?