Answer: I feel that 3 is the answer
Explanation: Let there be 2 objects, A and B
A is at height of 5m whereas B is at height of 15m
so over here let the gravitational potential energy of A be x
and since B is 3 times higher than A B=3x
Since, earth is considered to be the point where gravitational potenial is 0
So hence forth and object 3 times up will have 3 times the gravitational potential energy of A
The initial force between the two charges is given by:

where k is the Coulomb's constant, q1 and q2 the two charges, d their separation. Let's analyze now the other situations:
1. F
In this case, q1 is halved, q2 is doubled, but the distance between the charges remains d.
So, we have:

So, the new force is:

So the force has not changed.
2. F/4
In this case, q1 and q2 are unchanged. The distance between the charges is doubled to 2d.
So, we have:

So, the new force is:

So the force has decreased by a factor 4.
3. 6F
In this case, q1 is doubled and q2 is tripled. The distance between the charges remains d.
So, we have:

So, the new force is:

So the force has increased by a factor 6.
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Accuracy?
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