A pair of electrically charged objects attract each other with a force of 4 N when they are a distance of 3 m apart. If their charges stay the same, then what will be the attractive force between them when they are 6 m apart

1 N

Explanation:

From coulomb's law,

The force of attraction between two charges is inversely proportional to the square of the distance between the charges.

From the question,

Assuming the charges are the same in both case,

F ∝ /r² Equation 1

Fr² = k

F'r'² = Fr² Equation 2

Where F' = First Force, r'² = First distance, F = second force, r² = second distance.

make F the subject of the equation,

F = F'r'²/r² Equation 3

Given: F' = 4 N, r' = 3 m, r = 6 m

Substitute into equation 3

F = 4(3²)/6²

F = 36/36

F = 1 N

the part of the wave he is travelling on is the crest