1.) A 62 kg person runs up a flight of stairs whose vertical height is 11.7 m. I

Question

1.) A 62 kg person runs up a flight of stairs whose vertical height is 11.7 m. In how much time does she have to do that to use energy at the rate of one horsepower? (1 horsepower = 746 J/s)

1b.) Is this a realistic possibility? (The record time for climbing the 381 m of the Empire State Building is 9 min 33s, corresponding to a power of 404 W.)

2.)A child is on a swing that starts from rest at a point 1.7 m above the lowest point. The mass of the child together with the swing is 28 kg. Without a push the swing does not come back to the same height, but stops at a point 58 cm lower. How much energy does the father have to supply with each push if the swing is to come back to its original height of 1.7 m above the lowest (central) position?

Explanation / Answer

1a)
Work done, W = m*g*h
=62*9.81*11.7
=7116.2 J
P = W/t
746 J/s = 7116.2 J/t
t = 9.54 s
Answer: 9.54 s

1b)
Since maximum power achieved is just 404 W
but our case has power of 746 W which is more than maximum that can be acheived
This is not a realistic possibility

I am allowed to answer only 1 question at a time

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