Question

You have a bag of cotton and an iron bar........can you say which one is heavier and why

Answer 1

Some will fall in trap (supposedly) and say that 1 kg iron weighs higher and then the questioner will smilingly say no, both will weigh the same as they are both 1 Kg. Well if you go for a bit more accuracy and practical experience, it is not true! 1kg of cotton will weigh slightly less than 1kg Iron.

Answer 2

the density (mass/m^3) is greater in ironand less in cotton so we can say iron is heavier. but in this case we don't know what is the size of iron bar or cotton bag.