Fletcher's Trolley (Hanging Mass Problem)

[Mike_Stokes]

Homework Statement

A 1.20kg object is placed on a smoothe level table and is attached to a hanging mass using a light string over frictionless pulley in a Fletcher's trolley arrangement. The 1.20kg object accelerates along the table at 2.31m/s^2 while the hanging object accelerates down at the same rate. Determine the

a. Mass of the hanging object

b. tension in the string

The Attempt at a Solution

I drew 2 FBDs with the forces acting on each individual mass.

We know that Fapp = Fg2 = T

What I can't figure out is a formula that rearranges the variables to find m2

For example, I know that a = F/∑m

But we don't know what ∑m is.

We could relate Fapp to Fg2, but to do that we'd need to know m2

We can relate T to Fapp or Fg2, but we'd need to know m2...

You can see my dilemma. I've tried a good 10 different formulas, and now I'm just spitballing. I have no idea how I am supposed to create a formula that tells us m2 without knowing F

Please help.

 

[paisiello2]

Care to share your FBD's?

 

[Mike_Stokes]

Actually, I had a friend help me. Thanks anyways though. It turns out I was forgetting to factor in Fnet (the masses are moving). Fnet would have had me using a formula like this.

m2a = m2g - m1a

And solving from there.

It's very clear I need to remember that T ≠ Fg/2 while it is moving, but that T = Fapp

/thread