What is the Constant Speed of an Elevator with a 14kW Motor and 1100kg Mass?

[A.J.]

Homework Statement

The motor of an elevator can produce 14kW of power, its mass is 1100kg. At what constant speed will the elevator rise?

Homework Equations

F=ma
W= Fd
P= w/t
Vav= d/t

The Attempt at a Solution

P= w/t
P= Fd/t
P= F * Vav
V= P/mg = 14000W/(1100Kg*9.8m/s^2)=1.29m/s

The book states the answer is 13m/s. I have no idea how I'm suppose to get this answer, please help. Thanks in advance.

 

[hage567]

Hmmm, seems like there is a factor of ten missing somewhere. Are you sure you are using all the right values? Perhaps the book is wrong.

 

[Päällikkö]

As you've derived, the equation P = Fv is correct, so it looks like a mistake in the book. An elevator going 13 m/s seems a bit fast if floors are approx. 5 meters apart.

 

[A.J.]

Ok thanks guys.