What is a force that opposes motion when two objects are in contact with each other called? A) Gravity B) Friction C) Force D) Energy

What the question is really describing

You are looking for the name of the contact force that resists sliding (or attempted sliding) between two surfaces.

Identifying the correct force

Friction is a force that acts parallel to the surfaces in contact and opposes relative motion (or the tendency to move). It comes from microscopic bumps and attractions between the surfaces.

Why the other choices are not correct

• A) Gravity: acts at a distance between masses, not specifically because surfaces touch.
• C) Force: too general, friction is a specific type of force.
• D) Energy: energy is not a force; it is a quantity measured in joules.

Quick example

When you push a book across a table, friction from the table pushes back against the book’s motion, slowing it down or requiring you to keep pushing to maintain speed.