Physics Work & Energy ETEA 2017
PMDC Verified Question 94 of 108
A man of mass 60 kg climbs up a 20m long staircase to the top of a building 10m high. What is the work done by him: Take \( g = 10 \text{ ms}^{-2} \)
A
12 KJ
B
6 KJ
C
3 KJ
D
None of the above
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 6 KJ
Concept:

Work done against gravity depends entirely on the vertical height gained, independent of the actual path taken (like the slope length of the stairs).

Formula:

$$ W = mgh $$

Solution:

  • Mass (\( m \)) = 60 kg


  • Vertical Height (\( h \)) = 10 m (Ignore the 20m staircase length; it is path-dependent data irrelevant for conservative gravitational work).


  • \( W = 60 \times 10 \times 10 = 6000 \text{ J} \)


  • Convert to kilo-joules: \( 6000 \text{ J} = 6 \text{ KJ} \)


Why other options are incorrect:

Using the slant length of the staircase (20m) instead of vertical height yields \( 60 \times 10 \times 20 = 12000 \text{ J} \) or 12 KJ (Option A), which is incorrect because gravity only acts vertically.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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