Help with question on forces with motion, tension, friction

[shadowofanub]

Homework Statement

http://img253.imageshack.us/my.php?image=workshownph1.jpg

Homework Equations

The equations and the problem, along with the attempt at a solution are shown in the picture above

The Attempt at a Solution

The attempt is in the picture as well. Thanks guys for looking at it and helping out in advance. I have no idea with these sorts of problems where to start or what I am doing wrong.

 

[LowlyPion]

Homework Statement

http://img253.imageshack.us/my.php?image=workshownph1.jpg

Homework Equations

The equations and the problem, along with the attempt at a solution are shown in the picture above

The Attempt at a Solution

The attempt is in the picture as well. Thanks guys for looking at it and helping out in advance. I have no idea with these sorts of problems where to start or what I am doing wrong.

Welcome to PF.
What are you given for the coefficient of friction?

 

[shadowofanub]

Welcome to PF.
What are you given for the coefficient of friction?

Thanks, its good to be here. Unfortunately all i am given is what is shown in the picture. I just assumed there was friction since it didn't say there wasn't... that's why its in my equations.

 

[LowlyPion]

Thanks, its good to be here. Unfortunately all i am given is what is shown in the picture. I just assumed there was friction since it didn't say there wasn't... that's why its in my equations.

Your equations are inaccurate. The tension must allow for the weight of both box and sled as the sinθ from the incline.

There should be a μ*m*g*cosθ between the box and the sled. When acceleration of the combined system exceeds that then it will slip. But not knowing that μ ... if it was frictionless on the sled it would slide with any tension on the rope.