Question
Download Solution PDFA girl of mass 40 kg climbs 50 stairs of average height 20 cm each in 50 s. Find the power of the girl. (g = 10
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFCONCEPT:
- Work done (W): When a force is applied on a body and there is a displacement of the body in the direction of force then the work is said to be done by the force. The SI unit of work is Joule.
Work (W) = Force (F) × Displacement (S)
- Potential energy (PE): The energy of a body due to its position is called potential energy.
PE = m g h
Where m is mass, g is the acceleration due to gravity and h is height.
- Power (P): The rate of work done is called power.
- The SI unit of power is the watt (W).
Power (P) = work done (W) / time (t) (P = W / t = J / s)
CALCULATION:
Given that:
Mass (m) = 40 kg
Number of stairs (N) = 50
Height of each stairs = 20 cm
Total height (h) = Number of stairs × Height of each stairs = 50 × 20 = 1000 cm = 10 m
Potential energy gained by the girl = PE = m g h = 40 × 10 × 10 = 4000 J
Work done = PE = 4000 J
Power (P) = Work done/Time taken = 4000/50 = 80 Watt
Hence option 3 is correct.
Last updated on Jul 17, 2025
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