- #1

PhyIsOhSoHard

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## Homework Statement

A cylinder with mass M and radius R and moment of inertia I is standing on a rough surface (the left part of the triangle).

A box with mass m is standing on a smooth surface (right part of the triangle).

The cylinger and box is connected by a massless rope over a massless pulley.

The cylinder starts from rest and then rolls. Find the velocity of the box at the top of the triangle.

## Homework Equations

Kinetic rotational and translational energy

Potential energy

## The Attempt at a Solution

I tried to solve this and then I looked at my facits but there was one thing I did not take account for in my energy equation.

This is my facit (point of reference for potential energy is at their start position):

Where "1" is their start positions and "2" is when the box reaches the top of the triangle.

The thing that I have problem figuring out is this part:

I know it's supposed to be the potential energy of the cylinder when the box reaches the top, but I have no idea how they reached that. I've been looking at the drawing for an hour and can't figure it out.