1. Nov 21, 2005

### Seiya

An object of unknown mass is hung on the end of an unstretched spring and is released from rest. If the object falls 4.27 cm before first coming to rest, find the period of the motion.

All i can figure out is that the maximum amplitude is a given and ocurrs when cos of (wt) is 1

from this i could know that v = -Aw if i had a value for time..... right now im really confused, any advice would be really helpful, thank you

2. Nov 21, 2005

### mezarashi

The equation for period of oscillation is $$T = 2\pi \sqrt{\frac{m}{k}}$$.

The information given let's you find a relationship between the mass and the spring constant. By the principle of conservation of energy:

PE1 + KE1 = PE2 + KE2

KE1 = 0 as the mass was hung at rest. PE1 = PEspring1 + PEgrav1: you can consider the h to be zero here, then both are zero as well.

Would you like to try the energy analysis at point 2, when it is at the bottom and the string is maximally stretched at 4.27 cm?

3. Nov 21, 2005

### Seiya

Thanks i really gotta start doing this problems earlier in the morning so i can think broader ;p

energy at the bottom:

-mgx+1/2w^2mx^2

conservation of energy

0 = PEbottom

T= 2piw

done

thank you