Solving Oscillation Questions: Calculating Mass and Frequency

[Eclypse]

'A block is attached to a vertical spring whose spring constant is 150 N/m. It is droped from rest with the spring at its natural length, and the block has a speed of 75.0 cm after droping a distance of 8 cm. Calculate the mass of the block.'

Now i know k = 150. v = 0.75 and x = 0.08. I also know k = mw^2. w = 2pi f but i cannot figure out how to get the angular frequency.



also...I know this one is probably very easy but i just can't figure it out:

'A block hangs from a spring and is set into vertical oscillation with an amplitude of 15 cm. During the motion, the minimum extension of the spring is 5.00 cm. Calculate the freqency of the motion.'

I know i have Xm and x, but i cannot relate them to frequency.

Any help would be greatly appriciated, thank you.

 

[dextercioby]

For the first problem,use the law of conservation of total mechanical energy.

For the second,i have no idea what they mean by "minimum extension"...

Daniel.

 

[Davorak]

When the block is at the peak of its height the spring is at minimum extension so the spring length would be 5 cm. Do you know the definition of angular frequency in oscillator problems? Here is a link that goes through the derivation near the end is the definition of angular frequency for harmonic oscillators.
http://www.slcc.edu/schools/hum_sci...chanical_oscillations/harmonicoscillator.html

 

[Eclypse]

it doesn't ask for the angular frequency, it asks for the frequency,


its acctually a multiple choice question giving me answers :

1.11 Hz
.501 Hz
1.21 Hz
.996 Hz
.736 Hz
to chose from :(

 

[Davorak]

Well there is a simple correlation between angular frequency and frequency which is also given on the link above.