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For the same pair of surfaces, how do static and kinetic friction compare?
AThey are always exactly equal
BStatic friction is far weaker
CKinetic friction is far stronger
DStatic friction is usually greater
Answer & Solution
Correct answer: D. Static friction is usually greater
1. Static friction acts while the surfaces are still at rest relative to each other.
2. Kinetic friction acts once they are sliding.
3. For the same pair of surfaces the static value is usually the greater of the two.
4. That is why a crate takes a bigger push to start than it does to keep going.
_Source: OpenStax College Physics (CC BY 4.0), Ch 5 "Further Applications of Newton's Laws: Friction, Drag, and Elasticity", section Friction_
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