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## Homework Statement

A small mass m is pulled to the top of a frictionless halfcylinder (of radius R) by a cord that passes over the top of the cylinder. (a) If the mass moves at a constant speed, show that [tex]F=mg cos(\theta)[/tex]. The angle is between the horizontal and the radius drawn to the mass.

(b) By directly integrating

[tex]\int{Fds}[/tex]

find the work done in moving the mass at constant speed from the bottom to the top of the half-cylinder. Here ds represents an incremental displacement of the small mass.

## Homework Equations

## The Attempt at a Solution

The a-part was easy when I drew a diagram. The b-part is the one I'm struggling with. With the Work-Energy theorem I get that the work done by F is mgR. But what integral should I compute and why? Have no idea whatsoever..