Work Done Against Friction On An Incline
A wooden crate of mass 10 kg is dragged 5 m up a rough incline by a force, and friction exerts a constant 12 N opposing the motion along the surface. How much work is done against friction alone during this displacement?
Select the correct option:
Solution
60 J
As explained in NCERT Class 11, Chapter 6 (Work, Energy and Power), the work done against a constant friction force is the product of that force and the distance moved along the surface, since friction always acts opposite to the direction of motion. Here the friction force is 12 N and the displacement along the incline is 5 m, so the work done against friction is W = 12 × 5 = 60 J. This energy is dissipated as heat and is independent of the incline angle, depending only on the friction force and path length. The option 120 J doubles the result without cause. The option 50 J ignores the friction value and uses mass times something incorrect. The option 600 J wrongly multiplies in the mass of 10 kg. A sanity check: friction work depends on the actual distance travelled, not displacement between endpoints, and 60 J of heat for dragging a modest crate five metres is reasonable.
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About This Question
- Subject
- physics
- Chapter
- work, energy and power
- Topic
- work done against friction on an incline
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
60 J
As explained in NCERT Class 11, Chapter 6 (Work, Energy and Power), the work done against a constant friction force is the product of that force and the distance moved along the surface, since friction always acts opposite to the direction of motion. Here the friction force is 12 N and the displacement along the incline is 5 m, so the work done against friction is W = 12 × 5 = 60 J. This energy is dissipated as heat and is independent of the incline angle, depending only on the friction force and path length. The option 120 J doubles the result without cause. The option 50 J ignores the friction value and uses mass times something incorrect. The option 600 J wrongly multiplies in the mass of 10 kg. A sanity check: friction work depends on the actual distance travelled, not displacement between endpoints, and 60 J of heat for dragging a modest crate five metres is reasonable.
This easy difficulty physics question is from the chapter work, energy and power, covering the topic of work done against friction on an incline. It appeared in the 2025 exam.
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