Before Pluto was discovered, it was predicted. Astronomers had observed that massive objects can affect the orbits of its neighbors, and, after seeing deviations in the orbits of Uranus and Neptune, assumed something substantial existed beyond their orbits.
When Pluto was spotted, it was thought to be the predicted object and was identified as a ninth planet.
A few decades later, astronomers started discovering more and more objects around other stars and didn’t know whether to call them planets or not. There appeared to be a need to define what a planet means, and that led to what some people consider Pluto’s demotion to a dwarf planet.
The International Astronomical Union decided that full-sized planets must orbit the sun, have a round shape, and have cleared their orbits of other objects. Pluto fulfills the first two criteria, but not the third.
It still goes around the sun, it’s round enough, it’s got moons, and behaves like a planet, but the idea is that Pluto did not form the same way as the rest of the planets. Pluto’s orbit is both eccentric and inclined more than the rest of the planets by about 17 degrees. That’s suggests something is different about this object.
This debate about whether to call it a planet or not is silly, because it doesn’t matter to Pluto what you call it. It is an interesting object, goes around the sun, and shows geology and an atmosphere.
There’s a tendency to define objects based on what they are now, but nothing is constant in the universe. There are some issues with the nomenclature, and a definition today may not apply to the same object tomorrow.
The velcocity equals acceleration times time
which is 50 ms per sec
ionic compound. The atom that lost the electron becomes a cation, and the atom that gains an electron becomes an anion. The cation and anion bond together because they have opposite charges to form an ionic compound. The question may be looking for just cation or anion, though.
Answer:h=7.22 m
Explanation:
Given
mass of firefighter 
Frictional Force 
average speed at bottom 
Let h be the height of Pole
net force on Firefighter is
therefore net acceleration is
using 
here
They turn into a liguid. it is the opposite of evaporation. it didn't get hotter, it got cooler
