Question

A sofa remains stationary even after applying some horizontal force. The frictional force is acting on the sofa is ____________ the magnitude of applied force.

• A. lesser than
• B. greater than
• C. equal to
• D. either greater than or equal to

Answer 1

The correct option is C equal to

Frictional force opposes relative motion between two surfaces in contact.
Since the sofa is stationary, the frictional force of equal magnitude acts opposite to the applied force in order to balance it. This type of frictional force is called static friction.
Static friction keeps an object at rest. It is a self-adjusting force that has a maximum limit.
When the applied force overcomes this maximum value of static friction, the object starts moving. After this, sliding friction comes into play.
Hence, the frictional force is equal to the magnitude of the applied force.