decide how the sketches below would be listed, if they were listed in order of decreasing force between the…

decide how the sketches below would be listed, if they were listed in order of decreasing force between the charges. that is, select \1\ beside the sketch with the strongest force between the charges, select \2\ beside the sketch with the next strongest force between the charges, and so on.\nnote for advanced students: since the units of each charge are not written, you may assume any convenient and reasonable unit, for example coulombs or multiples of e.
Answer
Explanation:
Step1: Recall Coulomb's law
The force between two charges is given by $F = k\frac{q_1q_2}{r^2}$, where $k$ is Coulomb's constant, $q_1$ and $q_2$ are the magnitudes of the charges, and $r$ is the distance between them.
Step2: Analyze the first - top - left sketch
Let the distance between the two charges of magnitude $|q_1|=|q_2| = 1$ be $r_1$. Then $F_1=k\frac{1\times1}{r_1^2}$.
Step3: Analyze the second - top - right sketch
The two charges are $|q_1| = 2$ and $|q_2|=1$. Let the distance between them be $r_2$. Then $F_2=k\frac{2\times1}{r_2^2}$.
Step4: Analyze the third - bottom - left sketch
The two charges of magnitude $|q_1|=|q_2| = 1$ and assume the distance between them is $r_3$. Since the grid is the same as the first sketch, if we assume the distance in the first sketch is $r_1$, and here the distance is larger than $r_1$ (by counting the grid squares), say $r_3>r_1$. Then $F_3=k\frac{1\times1}{r_3^2}$.
Step5: Analyze the fourth - bottom - right sketch
The charges are $|q_1| = 2$ and $|q_2| = 1$. Let the distance between them be $r_4$.
Step6: Compare the forces
Assume the grid squares represent a unit of distance. Comparing the magnitudes of the products $\frac{q_1q_2}{r^2}$ for each case. For the top - right sketch, with $q_1 = 2,q_2 = 1$ and a relatively small distance, it has the largest force. For the top - left and bottom - right sketches, the product $q_1q_2$ is 1 and 2 respectively, and the bottom - right has a smaller distance than the top - left in terms of grid squares, so the force in the bottom - right is larger than the top - left. The bottom - left has the smallest force as the charges are 1 and 1 and the distance is relatively large.
Answer:
Top - right: 1 Bottom - right: 2 Top - left: 3 Bottom - left: 4