Any number that can be rewritten as a simple fraction is a rational number. This means that natural numbers, whole numbers and integers, like 5, are all part of the set of rational numbers as well because they can be written as fractions, as are mixed numbers like 1
All rational numbers can be written as a ratio of two integers (a fraction). when divided out, they may be non-terminating (go on forever), but if they do, they will always be repeating. For example: 1/2 divides out to 0.5 exactly. 1/3 divides out to 0.33333.....
[all of the above] 15kg box moving at same speed as 10kg box obviously has more inertia/energy and ogbects in motion will keep going at same velocity until acted upon by an outside force such as friction or it slamming into stuff and such