Answer:
The net force on the box is 2 N to the left.
The box will move to the left.
The acceleration on the box is 0.5 m/s^2 to the left.
Explanation:
Let's say movement to the right is positive and left is negative.
Bob: +10 N
John: -12 N
Add those together and you get a net force of -2 N, and the negative sign means that the box is moving to the left.
For the acceleration:
Fnet = ma
-2 = (4 kg)a
a = -0.5 m/s^2
Again, the negative sign in this answer means the box is being accelerated to the left.
The electrostatic force between the two ions is 
Explanation:
The electrostatic force between two charged particle is given by Coulomb's law:

where
is the Coulomb's constant
are the two charges
r is the separation between the two charges
In this problem, the ion of sodium has a charge of

while the ion of chlorine has a charge of

And the distance between the two ions is

Substituting, we find the electrostatic force between the two ions:

where the negative sign simply means that the force is attractive, since the two ions have opposite charge.
Learn more about electrostatic force:
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brainly.com/question/4273177
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An atom's mass number equals the number of protons plus the number of neutrons.
Hope this helps! (:
Answer:
The magnetic field is strongest at the center and weakest between the two poles just outside the bar magnet. The magnetic field lines are densest at the center and least dense between the two poles just outside the bar magnet.
Explanation: