The simplified model of the elevator is shown in Figure A. Considering the factors of safety, comfort and time saving, the elevator speed has to go through the process of increasing, constant and decr

The simplified model of the elevator is shown in Figure A. Considering the factors of safety, comfort and time saving, the elevator speed has to go through the process of increasing, constant and decreasing. (1) The height of the elevator rising is h=48m, and the time it takes is t-6s.

The average speed of the elevator rising is v = st = 48m6s = .8m/s;

(2) Work done with a tensile force of -4m: W1=F1h1=2.5×14N×4m=1.×15J,

Work done with a tensile force of 4-44m: W2=F2h2=2.×14N×4m=8.×15J, <

(3) Power of pulling force: p = WT = 9.6× 15J6s = 1.6× 14W.

Answer: (1) The average speed of elevator ascending is .8m/s;

(2) the work done by pulling force is 9.6× 15 j;

(3) The power of pulling work is 1.6× 14 W. 。