Question

explain that gravitational force is the dominant force determining motions in the solar system and in particular keeps the planets in orbit around the sun

Answer 1

Since this is not my area of expertise, I searched Google under the key words "<I>gravity 'solar system' movement</I>" to get these possible sources:

(Broken Link Removed)
http://en.wikibooks.org/wiki/Wikijunior_Solar_System/About_gravity,_mass,_and_weight
http://en.wikipedia.org/wiki/Solar_system
http://www.ctreg14.org/uploaded/faculty/npratt/8-3_science_unit.pdf
http://www.earthmatrix.com/sciencetoday/view_solar_system.html

In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.

I hope this helps. Thanks for asking.

Answer 2

I don't know what to say here. Of the forces known to exist in nature
gravity, electrical/magnetic, nuclear strong, and nuclear weak force, gravity is the only force possible.

If you were trying to explain planetary motion, then the orbits result because the force of gravity is just sufficient to change the motion of the planet to keep it in the same orbit. If it were less, the planet would hurl into space, if it were greater, the planet would fall into the Sun. The why of this is in the language of mathematics of Newtons's laws, and before him, Kepler's laws, and numerous Greeks who studied the laws and math of conic sections.

Answer 3

what are the role of the electrons in ionic bonds,covalent bonds and metallic bonds?