Motion/Time Question

  1. A hotel elevator ascends 230 m with a maximum speed of 5.8 m/s. Its acceleration and deceleration both have a magnitude of 1.0 m/s2.

    (a) How far does the elevator move while accelerating to full speed from rest?
    I got this part:

    x = v/2a = 5.8/2(1) = 5.82/2 = 16.82 m

    (b) How long does it take to make the complete trip from bottom to top?


    I broke the problem up into three sections: the elevator going up (1.0 m/s2), the elevator at rest (0), and the elevator coming back down (-1.0 m/s 2). I know that the elevator goes 230 m up and then 230 m down, but I cannot figure out which kinematic equation to use or if I need to use calculus (I have limited calculus knowledge).
     
  2. jcsd
  3. lewando

    lewando 1,077
    Gold Member

    Think about how an elevator operates as it goes up: it accelerates, travels at constant speed for a while, then decelerates. Same 3 phases on the down trip. Don't worry about the elevator at rest part--assume it goes up, stops for less than an instant, then goes back down.
     
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