Find force link 3 exerts on link 2

[jturn]

Homework Statement

A chain consisting of five links, each of mass 0.105 kg, is lifted vertically with a constant acceleration of a = 3.5 m/s2. Find the magnitude of the force that link 3 exerts on link 2.

Homework Equations

F = ma

The Attempt at a Solution

I did:
F = ma
FU - (0.105 * 3)(9.8) = (0.105) * 3.5
FU = 4.19 N

where FU is the force pulling up, (0.105*3) is the mass of the link's 5, 4, and 3 weighing down on link 2 (mg=weight) and then the mass*accel on the other side.

This is wrong. why? and how do i get the right answer?

 

[jturn]

does no one know how to do it? ...if it helps. i found the force required to move the top link at that acceleration to be 6.98 N...at it was the right answer...

 

[PhanthomJay]

Homework Statement

A chain consisting of five links, each of mass 0.105 kg, is lifted vertically with a constant acceleration of a = 3.5 m/s2. Find the magnitude of the force that link 3 exerts on link 2.

Homework Equations

F = ma

The Attempt at a Solution

I did:
F = ma
FU - (0.105 * 3)(9.8) = (0.105) *3[/color] *3.5
FU = 4.19 N OK[/color]

where FU is the force pulling up, (0.105*3) is the mass of the link's 5, 4, and 3 weighing down on link 2 (mg=weight) and then the mass*accel on the other side.

This is wrong. why? and how do i get the right answer?

It looks like your calculation and answer is correct, although you left out a 3 in an apparent typo omission (see above in red). Unless, the links are numbered 1 thru 5 bottom to top, rather than 1 thru 5 top to bottom??