How long will you wait for an elevator?
Q. So I am going to do my best to explain this problem, but feel free to add any variables I may have left out... A hotel has n elevators and m floors. Each floor has a height of h. Each elevator travels at some constant velocity v (for convenience let the units of v be ft/s). Assume the elevator does not stop until it reaches you. Assume that the elevators are on random floors when you push the button, and the CLOSEST elevator travels downward when called from a floor below and upward when called from a floor above. How many elevators are needed in order for the expected waiting time on the first floor to be 10 seconds? If you can generalize the problem even more, show me how. h has units of feet If you think that you need an exact v,… [cont.]
Asked by whitesox09 - Mon Oct 1 15:53:30 2007 - - 3 Answers - 0 Comments

A. Note that I'm slightly amending my earlier answer. If the nearest elevator is on the ith floor, then that elevator has to travel down i-1 floors to get to you. That will take ti = (i-1)*h/v seconds The probability that you'll have to wait ti seconds is the probability that the nearest elevator is on the ith floor and that no other elevator is nearer. The prob that the nearest elevator is on the ith floor = P(no elevators in 1st i-1 floors) - P(no elevators are in 1st i floors) = P(i) = [((m+1-i)^n - (m-i)^n] / m^n If T = waiting time P(T = ti) = P(i) = [((m+1-i)^n - (m-i)^n] / m^n Expected waiting time E(T) = ti*P(T=ti) = h/v * (i-1) * [((m+1-i)^n - (m-i)^n] / m^n This summation goes from i=1 to m In the example of n=4 elevators… [cont.]
Answered by Dr D - Mon Oct 1 16:16:47 2007

What happens if an elevator is set off at the earth's escape velocity?
Q. Suppose just a common elevator inside a building is set off at the earth's escape velocity. What happens to it and to the person inside it? The question has always boggled my mind. Any explanations in physics?
Asked by nice guy - Fri Jul 17 02:53:30 2009 - - 7 Answers - 0 Comments

A. There are a number of possibilities: a. If the escape velocity is achieved gradually with no more than 2g to 3g accleration than the person inside will fill uncomforable but will not die. However if accleration is very high the person's internal organs will collapse, blood vessels collapse, vital organs are subject to huge pressure and will collapse and die. b. More importantly the loss of oxygen will lead to the death of the person. Above 5 Km above the earth surface without acclimitisation is enough for the person to feel uncomfortable. Anything beyond 10 Km is enough for the person to die. Given that escape velocity is around 11km/sec. The person will meet an early end. c. The person is traveling in an elevator and at a higher speed… [cont.]
Answered by baldnbrainy - Fri Jul 17 03:34:55 2009

How much work did the elevator do on the safe?
Q. Workers load a 484 kg safe onto an elevator that lifts it 92 m to the twentieth floor of an office building. How much work did the elevator do on the safe? ___ J Work, Energy, and Power
Asked by Khoi - Fri Feb 9 20:35:44 2007 - - 1 Answers - 0 Comments

A. Work done = Force X Distance = mg x h Where: m = mass (484 kg) g = acceleration due to gravity (9.81 m/s ) h = 92 m Work done = 484 x 9.81 x 92 = 436,819,680 J (= 436,819.680 kJ)
Answered by Norrie - Fri Feb 9 20:51:28 2007