1. C. Gravitational attraction exists between the two objects.
Explanation:
Gravitational attraction is always exerted between two objects which have mass, and its magnitude is given by:

where G is the gravitational constant, m1 and m2 the masses of the two objects, and r the separation between them. Since the two objects have for sure non-zero masses m1 and m2, even if they are 20 miles apart, the value of the gravitational attraction F is non-zero, so the correct answer is C.
2. D. Two atoms come together to form a molecule.
Explanation:
this outcome is actually caused by the electrostatic forces between the two atoms, not by gravitational force. In fact, gravitational force becomes relevant only when the masses of the two objects involved are large enough: this is the case for planets, stars, galaxies, and objects in the universe. However, two atoms have very small masses, so the gravitational force between them is really negligible. On this smaller scales, the electrostatic force is much stronger than the gravitational force, so the electrostatic force is the real responsible for the formation of bonds between atoms.
Answer:
c. The temperature at which a glass transforms from a solid to liquid.
Explanation:
The glass transition temperature is said to be a temperature range when a polymer structure transition from a glass or hardy(solid) material to a rubber like or viscous liquid material.
The glass transition temperature is an important property that is critical in product design.
The Newton is defined as the:
C. Force that can give a 1-kilogram mass an acceleration of 1m/sec squared.
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Answer:

Explanation:
= Charge at 3000 m = 40 C
= Charge at 1000 m = -40 C
= 3000 m
= 1000 m
k = Coulomb constant = 
Electric field due to the charge at 3000 m

Electric field due to the charge at 1000 m

Electric field at the aircraft is
.