# Dynamics question - 2

1. Mar 16, 2009

### sArGe99

1. The problem statement, all variables and given/known data
http://s287.photobucket.com/albums/ll123/amalnathm/th_untitled.jpg

A uniform solid cylinder of mass m rests on two horizontal planks. A thread is wound on the cylinder. The hanging end of the thread is pulled vertically down with a constant force F. Find the maximum magnitude of force which does not bring about any sliding of the cylinder, if the coefficient of friction between the cylinder and the planks equal k. Which is the acceleration of the axis of the cylinder rolling down the inclined plane.

2. Relevant equations

3. The attempt at a solution
Direction of forces is giving me the headache again.

Force equation
F + mg - 2f = ma

Torque equation
(F - 2f) X R = $$I \alpha$$
f = k. (mg+F)
F - 2k (mg+F) = M a r / 2
F(1 - 2k) = 2kmg + M a r/2
F = (2kmg + m a r/2) / (1-2k)

Last edited by a moderator: Apr 24, 2017
2. Mar 16, 2009

### sArGe99

I need a bit of help with this please..

3. Mar 17, 2009

### sArGe99

BUMP!! Just keeping it on the top.