Free body diagram for a bag of coins suspended by an elastic band

[wizzle]

Homework Statement

Draw a free body diagram showing all the forces on the elastic band, and a free body diagram showing all the forces on the bag of coins

Homework Equations

F=-kx
F=mg

The Attempt at a Solution

I drew the forces on the elastic band as T = mg (m = mass of coins since the elastic band's mass isn't stated) upwards

and mg downwards

The forces I drew on the bag were F = kx upwards (the force of the elastic's stretch pulling proportionally upwards on the bag) and F = mg downwards (m = mass of coins)

If it were a rope attaching the bag to the ceiling I'd be ok but I'm a bit thrown off since it's an elastic band. Please let me know if this seems logical.

Thanks in advance for your help!

 

[LowlyPion]

Welcome to PF.

That sounds good.

 

[wizzle]

Wow, what a fast response! Thanks for the reassurance :)

 

[wizzle]

Hi, I just had one thought. This was from an experiment where coins were added one by one to a bag (attached to the elastic) and then the elastic stretched with each coin added (and I have to draw a free body diagram of the forces acting on the elastic and those acting on the bag).

Since the elastic band did move when the coins were added, am I wrong to say that these forces are in equilibrium? Maybe I should have instead said that the upward tension force on the elastic is equal to the spring force (F = kx)? Thanks again!