What is a difference between the electric force and gravitational force?

What is a difference between the electric force and gravitational force?

• A. Electric force can be attractive and repulsive while gravity is only attractive.
• B. Both forces are always attractive.
• C. Gravity can be attractive and repulsive.
• D. Electric force is always repulsive.

Answer: (A)

The main idea is that the electric force depends on the signs of electric charges, so it can either pull objects together or push them apart, while gravity depends only on mass and always pulls objects toward each other. According to Coulomb’s law, the force between two charges is proportional to the product of the charges and inversely proportional to the square of the distance; if the charges have opposite signs, the product is negative and the force is attractive, and if the charges have the same sign, the product is positive and the force is repulsive. Gravity, described by Newton’s law, is proportional to the product of the masses and inversely to the square of the distance; since masses are always positive, the force is always directed to pull the two objects together. So the key difference is that electric force can be attractive or repulsive, whereas gravity is only attractive. The other statements misstate this: electric force is not always repulsive, gravity is not repulsive, and both forces are not always attractive.

The main idea is that the electric force depends on the signs of electric charges, so it can either pull objects together or push them apart, while gravity depends only on mass and always pulls objects toward each other. According to Coulomb’s law, the force between two charges is proportional to the product of the charges and inversely proportional to the square of the distance; if the charges have opposite signs, the product is negative and the force is attractive, and if the charges have the same sign, the product is positive and the force is repulsive. Gravity, described by Newton’s law, is proportional to the product of the masses and inversely to the square of the distance; since masses are always positive, the force is always directed to pull the two objects together. So the key difference is that electric force can be attractive or repulsive, whereas gravity is only attractive. The other statements misstate this: electric force is not always repulsive, gravity is not repulsive, and both forces are not always attractive.