Simple Harmonic Motion and hung spring

[grandprix]

Homework Statement

A spring is hung from the ceiling. A 0.450-kg block is then attached to the free end of the spring. When released from rest, the block drops 0.150 m before momentarily coming to rest. (a) What is the spring constant of the spring? (b) Find the angular frequency of the block’s vibrations.

Homework Equations

Ei = Ef

\omega = sqrt (k/m)

The Attempt at a Solution

I can't figure out how to find part A. I know that once I find that I take that value and plug it into equation 2 to solve for the angular frequency.

 

[Cyosis]

During the entire motion of the spring two forces act on the block, which two forces?. During the instant the block is at rest how are these two forces related to each other?

 

[grandprix]

gravity on the block and tension on the spring?

 

[Cyosis]

Technically gravity and the restoring force of the spring. What about my second question?

 

[grandprix]

sum of the forces = -kx

right?

 

[Cyosis]

No, the sum of the forces=ma. During the instant the block is at rest, which force pulls harder, gravity or the restoring force?

 

[grandprix]

gravity

 

[Cyosis]

If gravity was pulling harder then why is the block at rest? If it was pulling harder it should be moving down. So same question again!

 

[grandprix]

Oh jeez i was making a careless mistake, I got the answer now!