It's not so much a "contradiction" as an approximation. Newton's law of gravitation is an inverse square law whose range is large. It keeps people on the ground, and it keeps satellites in orbit and that's some thousands of km. The force on someone on the ground - their weight - is probably a lot larger than the centripetal force keeping a satellite in orbit (though I've not actually done a calculation to totally verify this). The distance a falling body - a coin, say - travels is very small, and over such a small distance gravity is assumed/approximated to be constant.
Mass and distance
If mass is doubled, the force of gravity between the objects is doubled
Answer:
A body is said to be moving with uniform speed, if it covers equal distances in equal intervals of time. ...
Answer:B
Explanation:
Option A:
In the nuclear reactions,neutron can be split into proton an electron.
In this case,the number of protons are increasing,increasing the atomic number.
Hence,the atomic number is not conserved.
Option B:
In any reaction the sum of number of neutrons and number of protons remain constant before and after the reaction.
Option C:
The mass number may change for the atoms.For example 
emission reduces the atomic number by 
Option D:
In the nuclear reactions,neutron can be split into proton an electron.
So,they number of neutrons may change.
Explanation:
when a main-sequence star exhausts its core hydrogen fuel supply the core starts to shrink ( lack of fusion reactions) and the rest of the star starts to expands. The fusion reaction leaves the main sequence and begin to fuse helium in a shell outside the core. This mass stars become red supergiant and then evolve to become blue super giant.
