A descending elevator is subject to a constant rate of acceleration,dropping 50.0 m as it goes from an initial velocity of 15.0 m/s downward,to rest.As a percentage of the occupants' masses,what is their apparent weight?
A)66%
B)77%
C)100%
D)123%
E)134%

Question

Quizplus · Accepted Answer

The equation for the final velocity of the elevator can be given by:
v^2 = u^2 + 2as
where u = 15 m/s (initial velocity), s = -50 m (distance dropped), a = acceleration of the elevator, and v = 0 m/s (final velocity)
0 = 225 - 2a(50)
a = 2.25 m/s^2

The apparent weight of the occupants can be calculated using the equation:
Fapp = Fg - ma
where Fapp = apparent weight, Fg = gravitational force (mg), m = mass of the occupant, and a = acceleration of the elevator
Fg = mg = 9.81 m/s^2 * m
Fapp = ma = (9.81 m/s^2 * m) - (2.25 m/s^2 * m)
Fapp/Fg = (9.81 - 2.25)/9.81 = 0.77 or 77%
Therefore, the answer is D) 123%.

A Descending Elevator Is Subject to a Constant Rate of Acceleration,dropping