Spring mass help-desperate

1. Dec 7, 2003

bard

spring mass help--desperate

A 0.35-kg mass at the end of the vibrates 3 times per second with an amplitude of 0.15m. Determine (a)the velocity when it passes the equilibrum point (b)the velocity when it is 0.10m from the equilibrum point(c)the total energy of the system(d)the equation describing the moiton of the mass assuming that at t=0, x was maximum

ok i know that v=sqrtk/m(A^2-x^2)

the velocity would be V=sqrtk/m(0.15^2-0)

V=sqrtk/0.35(0.15^2-0)---other than that im am stuck can someone help

Thnx

2. Dec 7, 2003

Staff: Mentor

Find the spring constant k from the frequency f:

f = 1/(2&pi;) &radic;(k/m)

3. Dec 7, 2003

bard

ok i found K as 1.27 and plugged it back so \

so i got the velocity as 0.28m/s is this right

so then the velocity from 0.1 m from equibium would be

.78m/s

c) total energy of the system would be 1/2KA^2=0.014--dosent make sense

thnx

4. Dec 7, 2003

Staff: Mentor

I think you messed up the calculations. Do them over.

Here's a practical hint. For a and b, you can just use the value of &radic;(k/m) from the equation I gave. (No need to plug in k and m.) Less chance of calculation error.

5. Dec 7, 2003

bard

ok i got v=1.59 for part A and v=1.18 for part b

how do i find the total energy of the system?

6. Dec 7, 2003

Staff: Mentor

I get different answer for the speeds.

The total energy equals the spring potential energy at maximum compression.