What Is the Minimum Mass Needed to Move the Block in a Pulley System?

[jorcrobe]

Homework Statement

A block with mass, m1 = 5.5 kg rests on the surface of a horizontal table which has a coefficient of static friction of μs = 0.52. This block is connected to another block by a pulley system and it hangs vertically under the influence of gravity, g. The hanging block has mass m2.

What is the minimum mass, m2, that will cause the system to move?

Homework Equations

f_sum=ma

The Attempt at a Solution

I figured that the tension force must be equal to the force of static friction in order for the block to begin moving. I'm unsure where I should go from here.

 

[jorcrobe]

I have found that m2 = F_t/(g-a)

I figure that at that instant a = 0?

making m2 = 2.86

 

[LawrenceC]

If m2 exceeds 2.86 kg, motion will occur.