Suppose the free-fall acceleration at some location on earth was exactly 9.8000 m/s2. What would it be at the top of a 1100-m-tall tower at this location?

The sun's gravitational pull is weaker on the planets that are closer to it, i think.

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other