Work Done By Friction
Mediumphysics
A 2 kg block slides 3 m on rough horizontal surface (μ_k = 0.4, g = 10). Work done by friction?
Select the correct option:
Solution
Incorrect! Answer:
-24 J
- Friction Force: fk=μkN. For a horizontal surface N=mg.
- Calculation of Force:
- fk=0.4×(2×10)=8 N.
- Directionality: Friction always acts opposite to the direction of motion, so the angle θ=180∘ (or cosθ=−1).
- Work Calculation:
- W=fk×d×cos(180∘)
- W=8×3×(−1)=−24 J.
- Outcome: Kinetic friction does −24 J of work (energy is removed from the system).
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About This Question
- Subject
- physics
- Chapter
- work, energy and power
- Topic
- work done by friction
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
-24 J
- Friction Force: fk=μkN. For a horizontal surface N=mg.
- Calculation of Force:
- fk=0.4×(2×10)=8 N.
- Directionality: Friction always acts opposite to the direction of motion, so the angle θ=180∘ (or cosθ=−1).
- Work Calculation:
- W=fk×d×cos(180∘)
- W=8×3×(−1)=−24 J.
- Outcome: Kinetic friction does −24 J of work (energy is removed from the system).
This medium difficulty physics question is from the chapter work, energy and power, covering the topic of work done by friction. It appeared in the 2025 exam.
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