Which is an example of a contact force?

• A. Gravity.
• B. A hand pushing an object.
• C. Magnetic attraction.
• D. Electrostatic force.

Answer: (D)

The main idea here is distinguishing contact forces from non-contact (action-at-a-distance) forces. A hand pushing an object is a contact force because the force arises from direct physical touch between the hand and the object; the interaction at the point of contact transmits energy and momentum, causing the object to accelerate.

Gravity, magnetic attraction, and electrostatic force act without touching. Gravity pulls objects toward Earth from a distance through the gravitational field; magnetic attraction works through magnetic fields between objects without requiring contact; electrostatic force operates through electric fields between charged objects. These are non-contact forces.

So the example that best illustrates a contact force is the hand pushing an object.