A girl whose mass is 120kg, climbs up 5steps each of height 15cm in 10 sec.calculate the power expended
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Answer:
Given that:
- Mass of the girl = 120 kg
- Steps of stair = 5 steps
- Height of each step = 15 cm
- Time taken = 10 second
To determine:
- Power expended by her
Solution:
- Power expended = 90 Watts
→ Firstly let us convert cm into m!
==> 1 m = 100 cm
==> 1 cm = 1/100 m
==> 15 cm = 15/100 m
==> 15 cm = 0.15 m
- Therefore, height of each steps of the stairs = 0.15 m!
→ Now let us convert mass into weight!
==> Weight = Mass × Acceleration due to the gravitational force of earth (gravity)
==> Weight = 120 × 10 (9.8 m/s² ≈ 10 m/s²)
==> Weight = 1200 Newton
- Therefore, the weight or the force = 1200 Newton.
→ Now let us calculate height of 5 steps of the stairs!
==> 5 × 0.15
==> 0.75 metres
- Therefore, the total displacement = 0.75 metres.
→ Now let us calculate the power!
==> Power = Work done/Time taken
==> Power = Force × Displacement/Time
==> Power = 1200 × 0.75/10
==> Power = 120 × 0.75
==> Power = 90 Watts
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