If it were possible for an object to fall freely near the surface of the Earth,
-- The direction of its velocity would always be "down"; that is, toward the center of the Earth.
-- The size of its velocity would continually increase, at the rate of 9.8 meters per second for every second it falls.
It'd be an unbalanced force
Because the number of valence electrons of an element determines the properties and in particular the reactivity of that element.
In fact, elements of the first group (i.e. only one valence electron) have high reactivity, because they can easily give away their valence electron to atoms of other elements forming bonds. On the contrary, elements of the 8th group (noble gases) have their outermost shell completely filled with electrons, so they do not have valence electrons, and they have little or no reactivity at all.
We can conclude that it is a longitudinal wave because the wave is traveling through a medium displacing particles<span>
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