In: Physics
Which of these statements comparing electric and gravitational forces is correct?
(a) The direction of the electric force exerted by one point particle on another is always the same as the direction of the gravitational force exerted by that particle on the other.
(b) The electric and gravitational forces exerted by two particles on each other are inversely proportional to the separation of the particles.
(c) The electric force exerted by one planet on another is typically stronger than the gravitational force exerted by that same planet on the other.
(d) None of the above
Use the expressions for the electric force and gravitational force to identify the correct statement.
The electric force is given by,
FE = kq1q2/r2
Here, k is the constant, q1 and q2 is the charge of the two particles, and r is the separation between the particles.
The gravitational force between the two particles is given by,
Fg = Gm1m2/r2
Here, G is the gravitational constant and m1, m2 is the mass of the two particles.
The direction of the electric force depends on the charge.
Hence, we can’t say the direction of the electric force is always same as the direction of the gravitational force.
Therefore, the statement (a) is incorrect.
The electric force is stronger than the gravitational force for the elementary particles but it is weaker for the planetary system.
Therefore, the statement (c) is incorrect.
From the above two expressions, the electric and gravitational forces are inversely proportional to the separation of the two particles.
Therefore, the statement (b) is correct.
The statement (b) is correct.