The question asks us to identify which of the given options is not a conservative force. In order to do this, let`s examine each option.
Option 1: Frictional force
Frictional force is a non-conservative force. It acts opposite to the direction of motion and tends to dissipate energy as heat. Therefore, option 1 is a correct answer.
Option 2: Electric force
Electric force is a conservative force. It is central in nature, meaning it depends only on the distance between the charges and follows the inverse square law. Therefore, option 2 is not the correct answer.
Option 3: Gravitational force
Gravitational force is a conservative force. It is central in nature, follows the inverse square law, and does not dissipate energy. Therefore, option 3 is not the correct answer.
Option 4: Spring force
Spring force is a conservative force. It is an example of a Hooke`s law force and depends only on the displacement of the spring. It does not dissipate energy. Therefore, option 4 is not the correct answer.
In conclusion, option 1 (frictional force) is the correct answer as it is not a conservative force.