Answer:
(a) the force is 8.876 N
(b) the magnitude of each charge is 4.085 μC
Explanation:
Part (a)
Given;
coulomb's constant, K = 8.99 x 10⁹ N.m²/C²
distance between two charges, r = 10 cm = 0.1 m
force between the two charges, F = 15 N
when the distance between the charges changes to 13 cm (0.13 m)
force between the two charges, F = ?
Apply Coulomb's law;

Part (b)
the magnitude of each charge, if they have equal magnitude

where;
F is the force between the charges
K is Coulomb's constant
Q is the charge
r is the distance between the charges

Density applies to many if not all aspects of life. With density you can explain why ice floats. You can explain why oxygen is on the earth, and not floating around in space( or being replaced by another gas). You can also explain why heat rises while cold air sinks.
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.
5m/s
100m
Explanation:
Average speed is sum of distance distance traveled in a given time by a body.
Average speed= 
Distance = 20m
time = 4s
Average speed =
= 5m/s
For the spaceship;
Distance covered = speed x time
Speed = 50m/s
time = 2s
Distance covered = 50 x 2 = 100m
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Answer:
Distance = 85.3 miles
displacement = 0
Explanation:
The total distance covered to grandma's house is 42.6 miles as recorded by the odometer. The same distance would be covered when returning to the base. Hence;
Total distance for the round trip = 42.6 + 42.6 = 85.2 miles
Since the trip was a round trip, the displacement is zero because the family returned to their initial location.