Which of the following is NOT a non-contact force?

Friction

The correct answer is option 3. Friction.

The force that is NOT a non-contact force is Friction.

Friction is a contact force that arises when two surfaces rub against each other. It opposes the relative motion or tendency of such motion between the surfaces. Unlike gravitational, electrostatic, and magnetic forces, which can act between objects without physical contact, friction requires direct contact between surfaces. Therefore, friction is not classified as a non-contact force.