How is Work Calculated for Pulling Up a Curtain?

[Uku]

Homework Statement

A curtain is rolled up a thin rod. There is no friction. The length of the curtain is l=2m and weight is m=2kg. Find the work done.

EDIT: the mass is 1kg not 2.

Homework Equations

A=Fs

The Attempt at a Solution

The solution is A=9.81J The way I did it was that the work done is the area under the curve on the F/s plot. Since the force needed to pull drops linearly, I simply multiplied mg*l and then I divided that by two. Is this approach valid? The answer is correct.

 

[RTW69]

mg*L/2 equals 19.6 J are you saying that 9.81 J is supposed to be the correct answer? I assumed that the center of mass of the curtain was at L= 1 m and that mass was lifted 1 meter to the top of the window. Work = Force * distance * Cos(0)

 

[Uku]

I mistyped the mass, it is 1kg.