<span>1. Kuiper Belt object is made of frozen is made of frozen gas, ice, and dust that orbits in the outermost reaches of the solar system. Kuiper belt is a region which is filled with icy gaz bodies. Its structure is almost the same as the asteroid belt between Mars and Jupiter. Pluto, Makemake, Haumea are the officially recognized planets which are located in this region.
2. In my opinion, the most suitable option is: 3) The planets formed at the center of a collapsing spinning cloud of gas and dust. According to theory of solar system formation, the solar system appeared after a supernova (star explosion). A cloud of gas and dust was collapsed, and it caused a formation of a solar nebula.
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Explanation:
(a) Formula to calculate the density is as follows.

= 
= 
Now, calculate the charge as follows.

= 
=
C
or, = 101.06 nC
(b) For r = 6.50 cm, the value of charge will be calculated as follows.

= 
= 7.454 
Answer:
If the system consists of the block only, the work done by the gravity is negative.
If the system consists of the block and the earth the work done by the gravity is zero.
Explanation:
If the system consists of the block only, then the system experiences two external forces: one exerted by the hand that lifts the block vertically upward and other exerted by the earth (gravity), which is opposed to the movement of the system, so the work done by gravity is negative.
On the other hand, if the system consists of the block and the earth, then only exists a external force which is the exerted by the hand. So, the force exerted by gravity is zero.
If you remember the formula for potential energy,
then this question is a piece-o-cake.
<em>Potential energy = (mass) x (<u>acceleration of gravity</u>) x (height) .</em>
-- The object's mass is the same everywhere.
-- You said that the height is the same both times.
-- How about the acceleration of gravity ?
Compared to gravity on Earth, it's only 16.5 percent as much on the Moon.
So naturally, from the formula, you'd expect the Potential Energy to be less
on the Moon.