# What effect does the force of friction have on motion? a) it causes objects to accelerate b) it counteracts the acceleration of an object c) it prevents surfaces from sliding against each other

tjbrewer | Certified Educator

What effect does the force of friction have on motion?

a) It causes objects to accelerate.  While this is true, it is not the correct answer.  As a force, friction does cause an acceleration, but this force is only observed when a force is applied to an object that is in contact with matter other than the object.

b) It counteracts the acceleration of an object.  This is a common misunderstanding of what friction is.  Friction doesn't counteract anything.  Friction is a force and causes acceleration opposite to the velocity of an object in motion, where there is contact between the object and other matter.

c) It prevents surfaces from sliding against each other.  This is a paraphrase of the definition of friction, it is a force against the motion of an object in contact with other matter.