posted by HP on .
an escalator carries you from one level to the next in the airport terminal. the upper level is 4.5 m above the lower level, and the length of the escalator is 7 m. your mass is 60 kg.
how much work does the up escalator do on you when you ride it from the lower level to the upper level?
how much work does the does the down escalator do on you when you ride it from the upper level to the lower level?
the answer for the first is 2600 J and the second is -2600 J. i just don't know how to get there!
work=force dot distance where dot means the dot product. Dot product means the component in the same direction. Here force is mg, so the distance in that direction is 4m
Notice in the second, the movement is downward, gravity is doing the work, the escalator is absorbing it, hence the negative sign.
Work = potential energy of you
Work =mass *9.8 m/s *Height
Work = 60kg *9.8*4.5
Work =2646 J =2.646 kJ