There is a bell at the top of a tower that is 30 m high. The bell has a mass of 7.2 kg. Calculate its potential energy

You know how the first one if filled up like the objects do the same but with the other categories

The density of water is 1 g/cm cubed and in order for the pebble to sink its density has to be greater than the density of water and in order for the twig to float its density has to be less than the density of water

They are all solids.

Ithink about 50 % of an original isotope's number of atoms remain