# Difficult problem

1. Mar 2, 2006

### Kenchin

With a system where Block A is on a horizontal and Block B is over the edge connected by a rope on a pulley, block A has mass = 2.10 , block B has mass = 0.410 , and the rope connecting them has a nonzero mass 0.162 . The rope has a total length 1.08 and the pulley has a very small radius. Let d be the length of rope that hangs vertically between the pulley and block B. Ignore any sag in the horizontal part of the rope. The coefficent of static friction is .247. Find the distance necessary to start the motion of block A from rest.

Okay after I saw this problem I tried to set it up where the kinetic force of friction + the weight of the rope before the pully containing the equation .162-.162(1.08-d/1.08) [where d is the distance over the pulley] = .162(9.80)(d/1.08)+.410(9.80). I cannot get this to work, can anyone assist me by showing me where i went wrong?

2. Mar 2, 2006

### Integral

Staff Emeritus
It is impossible to help you.

You must provide the units with your numbers. Block A has a mass of 2.1 (Something) like wise your distances must carry the correct units. In order to complete this problem you must use some number for g, the acceleration due to gravity, it has different numbers depending upon the system of units. Since you have not told us what units you are working in we cannot check your numbers. Please post the complete problem.

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