Post-UTME Physics 2011 Objective — Question 3
Question 3 of 10 from the Post-UTME Screening (Post-UTME) Physics 2011 Objective paper, with the correct answer and a full explanation.
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A block and tackle system is used to lift a load of 20N through a vertical height of 10m. If the efficiency of the system is 40%, how much work is done against friction?
- A. 80J
- B. 120J
- C. 300JCorrect
- D. 500J
Explanation
Efficiency=output/input×100: 40=(20×10)/input×100, so input=500J. Work against friction=input-output=500-200=300J.
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