Which statement about static friction versus kinetic friction is true?

Which statement about static friction versus kinetic friction is true?

• A. Static friction never prevents motion
• B. Static friction prevents motion up to a limit; kinetic friction acts when an object slides, usually less than static friction
• C. Static friction is always greater than kinetic friction
• D. Static friction only occurs when an object is moving through a liquid

Answer: (B)

Static friction and kinetic friction describe how surfaces resist sliding past each other in two different ways. Static friction holds an object in place by adjusting its force up to a maximum value, matching the applied push to keep the object from moving. That maximum is the threshold: if the push stays below it, nothing slides. When the push is strong enough to surpass that limit, motion begins, and static friction gives way to kinetic friction. Once sliding, the friction force that resists movement is generally smaller and stays roughly constant as you continue to push, opposing the motion. So the statement is true because static friction prevents motion up to a limit, and once motion starts, kinetic friction acts, typically weaker than the maximum static friction. The other choices don’t fit: static friction can prevent motion (not never), it doesn’t require a liquid to occur, and while static friction is usually larger than kinetic friction, that relationship is not an absolute rule for every situation.

Static friction and kinetic friction describe how surfaces resist sliding past each other in two different ways. Static friction holds an object in place by adjusting its force up to a maximum value, matching the applied push to keep the object from moving. That maximum is the threshold: if the push stays below it, nothing slides.

When the push is strong enough to surpass that limit, motion begins, and static friction gives way to kinetic friction. Once sliding, the friction force that resists movement is generally smaller and stays roughly constant as you continue to push, opposing the motion.

So the statement is true because static friction prevents motion up to a limit, and once motion starts, kinetic friction acts, typically weaker than the maximum static friction. The other choices don’t fit: static friction can prevent motion (not never), it doesn’t require a liquid to occur, and while static friction is usually larger than kinetic friction, that relationship is not an absolute rule for every situation.