Stairs

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					Usually, it is easier for you to move up an inclined plane than climbing stairs of the
same height. Explain.



Usually,
(1) you feel uncomfortable if your body has to consume a lot of energy in a short
     period;
(2) the slope of stairs is larger than that of an inclined plane of the same height.


Suppose the height of the stairs and inclined plane is the same, h.



                          h



Assuming that you move up steadily in both cases. That means in any instant, the
vertical force to move up your body is just the same as your weight.
(If the upward force is larger than your weight, you will accelerate upwards at that
instant, and your movement is not steady.)

The work done to move up the stairs and inclined plane is also the same, W = m g h

Usually it takes longer time for you to move up an inclined plane. (usually!!)
i.e.      tin > tst               ( tin is the time for moving up inclined plane;
                                    tst is the time for climbing stairs )
Thus, Pst > Pin                   ( Pin is the power for moving up inclined plane;
                                    Pst is the power for climbing stairs )

Thus, in climbing stairs, you need to consume the same amount of energy in a short
period, you feel harder than moving up inclined plane of the same height.

				
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posted:11/18/2011
language:English
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