A 5.0 kg box is at rest on a horizontal floor. A horizontal force of 25 N is applied to the box, but it does not move. What is the magnitude of the static friction force acting on the box?
Show the answer and explanation
Correct answer
B. 25 N
Principle or equation
Newton's first law: if an object remains at rest, the net force on it must be zero. The applied horizontal force is balanced by the static friction force.
Why this answer is correct
The box is at rest, so the net horizontal force is zero. The applied force is 25 N to the right, so the static friction force must be 25 N to the left. Its magnitude is 25 N.
Example
If a 10 N force is applied to a stationary block and it doesn't move, static friction is 10 N.
This published item includes a stored explanation and passed the platform’s publication workflow. It is independent preparation material, not a claim of an official or recalled examination question.