# Homework Help: Urgent Help Needed

1. Sep 15, 2008

### dsptl

Urgent Help Needed!!!

Last edited by a moderator: May 3, 2017
2. Sep 15, 2008

### LowlyPion

Re: Urgent Help Needed!!!

Welcome to PF.

The key phrase here is "after some time".

You can assume from that that all the blocks will be moving together as one. You need not know what any of the compressions are because they are all moving together.

You have your weights (all of them together) reacting with a kinetic coefficient retarding motion. You have the total mass being accelerated, you have the total force.

Solve at will.

Last edited by a moderator: May 3, 2017
3. Sep 15, 2008

### dsptl

Re: Urgent Help Needed!!!

so basically:

along y axis: Fnet = ma = 0

n - mg = 0
n = mg = (20kg)(9.81)

along x axis: Fnet = ma

I have a question which will kinetic force go

is it 60N - Fk = ma? its other way around... -60N + Fk = ma

are there any other forces...and wht do with those N/m units numbers?

4. Sep 15, 2008

### LowlyPion

Re: Urgent Help Needed!!!

60N is being retarded by total weight times μ and that must equal Total Mass times acceleration.

Forget the spring constants and detents on the individual springs, because of the phrase "after some time".