I believe the best answer is law, as scientific laws are accepted to be true under the proper conditions.
Answer:

Explanation:
A charge located at a point will experience a zero electrostatic force if the resultant electric field on it due to any other charge(s) is zero.
is located at the origin. The net force on it will only be zero if the resultant electric field intensity due to
and
at the origin is equal to zero. Therefore we can perform this solution without necessarily needing the value of
.
Let the electric field intensity due to
be +
and that due to
be -
since the charge is negative. Hence at the origin;

From equation (1) above, we obtain the following;

From Coulomb's law the following relationship holds;

where
is the distance of
from the origin,
is the distance of
from the origin and k is the electrostatic constant.
It therefore means that from equation (2) we can write the following;

k can cancel out from both side of equation (3), so that we finally obtain the following;

Given;

Substituting these values into equation (4); we obtain the following;


Answer:
A derived quantities is terms of the 7 base quantities via a system of quantity equations which are called SI derived units.
Explanation: there you go:)
Answer:
945 j
Explanation:
You have just given the ball kinetic energy, which is given by the following equation:
KE= 1⁄2 m v2 = 1⁄2 (2.1 kg)(30 m/s)2 = 945 Joules
Answer:
A. The sound wave will reflect off Buildings and automobiles.
Explanation:
This is because the sound waves would more likely propagate through diffraction through buildings and transmission through the air. It is also more likely to be absorbed by buildings than for multiple reflections to occur off buildings and automobiles. In the process of reflection, these materials would absorb the sound energy thereby reducing its ability to reflect.