Calculate the average speed of an automobile that travels 60km east and then 80km north in two hours

We need to calculate speed , so we don't need to consider direction.
speed =distance/time
=(80+60)/2
=70.

But if we were to calculate velocity,we would need to consider the direction.
The direction of resultant displacement would be in north east direction with displacement
=√60^2 +80^2
=100km

The average velocity=100/2=50kmph

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -

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