In a charming 19th-century hotel, an old-style elevator is connected to a counte
ID: 1497861 • Letter: I
Question
In a charming 19th-century hotel, an old-style elevator is connected to a counterweight by a cable that passes over a rotating disk 3.00 m in diameter (the figure(Figure 1) ). The elevator is raised and lowered by turning the disk, and the cable does not slip on the rim of the disk but turns with it.
Part A
At how many rpm must the disk turn to raise the elevator at 30.0 cm/s ?
Part B
To start the elevator moving, it must be accelerated at 1/8g. What must be the angular acceleration of the disk, in rad/s2?
Explanation / Answer
Part A )
since it is not slipping
V = RW
W= V/R
w = 0.3/1.5
w = 0.2 rad/sec
w = 1.9098 rpm
Part B)
a = R alpha
g/8 = 1.5 alpha
alpha = 0.8166 rad/s^2