850 N up - 750 weight down = m a up
m a = 100 N
a = 100/m up
Vinitial = - 25 000m/ 3600 s = - 6.94 m/s
v = Vi + a t
assume v = 0 at ground with no crash
0 = -6.94 + (100/m) t
if g = 9.81m/s^2
then m = 750 N / 9.81 = 76.5 kg
so
(100/76.5) t = 6.94
t = 5.31 seconds
A 750- N person steps on the weighing scale inside a moving elevator as it slows down to the ground floor. The person notices that his weight is 850 N while the elevator is decelerating How long will it take the elevator to reach the ground it it is moving at 25 km/h before the elevator started decelerating?
1 answer