Find the mass of a block on an inclined pulley

[mt05]

Homework Statement

Block A is traveling down an incline plane of 35 degrees at 2m/s. It's pulling a 4kg block with a pulley and rope. Coefficient of friction is.12. How heavy must block A be ?

Homework Equations

F=MA
F = WsinΦ + μWcosΦ
mgh = 1/2 mv^2 + WD to overcome friction
Vf^2 = u^2 + 2as

The Attempt at a Solution

I'm having a hard time thinking through this question. I know how to find the forces on an inclined plane and I understand that it needs to overcome the force of the 4kg block and accelerate it to 2m/s. Whenever I see velocity I automatically think of the linear velocity and acceleration equations. I'm not even sure where to begin. I've tried the above equations but it seems like I'm always missing a value. If someone could point me in the right direction I will try and post on here.

thanks

 

[PhanthomJay]

Here is nothing in the problem that implies acceleration. It is moving at a constant speed of 2 m/s.

 

[mt05]

yes, thank you.

F = Fg + KE
F = (4)(9.81) + 1/2(4)(2^2)
F = 47.24 N (so this is required force that block A must pull in order to move 4kg box at 2m/s)

I'm struggling to think of finding the force that an unknown mass has.

 

[PhanthomJay]

yes, thank you.

F = Fg + KE
F = (4)(9.81) + 1/2(4)(2^2)
F = 47.24 N (so this is required force that block A must pull in order to move 4kg box at 2m/s)

I'm struggling to think of finding the force that an unknown mass has.

Your equation makes no sense. It is for starters dimensionally incorrect, since the gravity force is in Newtons and KE is in Newton-meters. And surely the angle of the incline comes into play.
You should start by drawing free body diagrams of each block, identify the forces acting on each, both known and unknown, and apply Newton’s laws. Which one of Newton’s laws applies for objects moving at constant velocity? You should end up with two equations with two unknowns, solve. The speed of the block is irrelevant.