Multiple choice

What happens when one object moves over the surface of another object?

  1. Surface of only upper object exerts force of friction on lower object.

  2. Surface of lower object exerts force of friction on upper object.

  3. Surface of both the objects exerts force on each other.

  4. Surface of both the objects exerts force in a direction opposite to each other.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

According to Newton's third law, when two surfaces slide against each other, BOTH surfaces experience friction forces. These forces are equal in magnitude but opposite in direction - each surface exerts friction on the other. Option A incorrectly suggests only the upper object exerts friction, option B incorrectly suggests only the lower object does, and option C is incomplete. Option D correctly captures that both surfaces exert friction forces in opposite directions.

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