Kinetic Friction
Kinetic friction does negative work because it:
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About This Question
- Subject
- physics
- Chapter
- laws of motion
- Topic
- kinetic friction
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
Opposes displacement direction.
Work done W by a force F is W=F⋅d=Fdcosϕ, where ϕ is the angle between force and displacement.
- Kinetic friction fk always acts in a direction opposite to the relative motion (slipping) of the surfaces.
- Therefore, the angle ϕ=180∘, and cos180∘=−1.
- W=fkd(−1)=−fkd, which is negative. Negative work means energy is being removed from the system, typically appearing as heat.
This easy difficulty physics question is from the chapter laws of motion, covering the topic of kinetic friction. It appeared in the 2025 exam.
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