question_answer 53)

                  Why is electrical power required at all when die elevator is descending? Why should there be a limit on the number of passengers in this case?                

Answer:

                  If electrical power is not given, elevator will fall freely under gravity. Therefore, to avoid the free fall of elevator under gravity, electrical power is needed. The maximum tension in die supporting cable of an elevator is given by \[T=m(g+a)\], where, m is the mass of passengers and 'a' is the acceleration of the elevator in the upward direction.